"A practical man can always make what he wants to do look like a noble sacrifice of personal inclinations to the welfare of the community. I've decided that I've got to be practical myself, and that's one of the rules. How about breakfast?" The Pirates of Ersatz, Murray Leinster

From your question I noticed a few things. Nominally, I completely agree with @mxyzplk's answer, so this should be in the way of an addendum.

It sucks to be the leader

In a RPG, it just completely sucks to be the leader. Most players when confronted with a plan, remember about fifteen percent of it for the first fifteen minutes. But they'll certainly remember when you deviate. Leaders get no additional responsibility and no perquisites, but they get all the blame.

In the military this is mitigated with the clear distinction between commissioned and non-commissioned officers. Not least because the isolation provides both support structures and necessary emotional distance (to a degree, of course). Being "elected" leader, especially with the pack dynamics of typical werewolf games is an extremely dubious honour that I'd flatly reject.

The fact that while you may be leader in character but not dominant over the player group makes things even stickier. You need to assert authority within the realm of the narrative without actually having that authority in reality. Again, something that will cause friction and resentment any way you cut it.

Depressing environments bleed emotions into play

The world of darkness does what it says on the tin. Having played in a horror game myself recently, the iconic themes of the world of darkness do not make for "happy" or, for that matter, validating game experiences in the main. (And, if they do, it's a violation of genre.) When you are faced with the stresses of being "leader" which are compounded by the stressors of the philosophies baked into the setting, no wonder you're having a rough time.

Some solutions:

On leadership:

Fundamentally, a gaming group is a relationship. Bad relationships that do not provide validation are a drain on mental and emotional resources. When they don't work, cut them off or change them. In your case, I'd play a game that's a bit lighter in tone and focus: a nice traditional dungeon crawl or similar heroic fantasy.

I'd also reject the leader role for all the reasons I outlined above. Or, if they force it upon you, demand the perquisites and authority that is concomitant with it: they can't have it both ways.

On the group:

I've found that group character creation creates a far more cohesive group. By having entangled backstories, the group can draw upon a deeper understanding of each others' characters, creating the basis for empathy and respect within the characters, instead of the necessary simulacrum imposed by players.

By articulating desired tropes, a "palette" (as Microscope) calls it, before the game begins, you'll be able to shape the narrative of the group in directions that you want to play. This allows you to avoid the nominally depressive tropes that come default with the setting (not limited to world of darkness) and describe a source for future characters to connect with the current group. Replacement characters, if they tie into the shared narrative, will continue to maintain the tropes and social trust.

Be practical:

As players, we shape our narratives to an amazing degree. Emulate Bron Hoddan in the Pirates of Ersatz. While playing, you will be aware of the desired practical outcome that will provide validation and satisfy your personal goals. With that outcome in mind, you then frame it in terms that suit both your character's narrative and the expected narratives of the other players such that they will act to reinforce your framing and thereby your outcome. If you fight their narrative control by "being a loner," it is difficult to achieve your own goals. If you help them work as a team and appear to sacrifice nobly on their behalf while executing your own goals... the entire process is smoother and more effective.

Note that I am not saying to lie. Instead, consider the causal constructions of your actions, the explanations for those actions to be an aspect of the role * separate* from the actions themselves. By manipulating the framing as well as the actions, you can provide the necessary hooks for the other players to support your version of reality, rather than rejecting it and, by extension, you.

Postscript

Looking at your comments to other questions, you should absolutely give this group two last tries. In the first trial (of one or two games), try a heroic romp where you can be "Big Damn Heroes." Require the players who need the spotlight be leader. In the second trial (again of one or two games), try a game where players can intrigue against each other (I'd recommend Ars Magica, but then again I recommend it for most things. Most games support PvP intrigue quite ably.) If neither game provides the validation you need and the spotlight the other players need, move on. Before you do anything, take a month break, sit down, relax, and try to game with some strangers. I'm pretty sure that if you go looking for games in the chat section of this site... someone will oblige. For more on the framing problem, I'd quite recommend Rule 34 by Stross, as it describes it in a delicious narrative context.

Unfortunately there's nothing within the rules that dictates how a Druid must act. Though, the introduction to the class clearly states

Druids are also concerned with the delicate ecological balance that sustains plant and animal life, and the need for civilized folk to live in harmony with nature, not in opposition to it. (PHB, pg.65)

Druids are also part of larger organisations, called Circles, the description of which includes this line:

Druids recognise each other as brothers and sisters. Like creatures of the wilderness, however, druids sometimes compete with or even prey on one another. (PHB, pg. 68. Emphasis mine)

There's no information on how to punish a druid for living in disharmony with his or her environment, but it seems clear that they believe in the natural order; the laws of nature. Even when it means the strong hunt and prey on the weak. A druid is certainly not forbidden to kill animals, especially if it's for their own survival. Hunting and preying is the natural way.

And they are certainly under no obligation to constantly care for all plants around them. But perhaps going out of their way to destroy them would cross the line, though.

A Character's behaviour is not governed by their class

One thing to keep in mind that a character's class is a mechanical term and used within the game to determine their capabilities. Within the world, their vocation may be quite different. Perhaps the Bard is simply a charismatic politician, swaying the populace with powerful speeches instead of moving song. Perhaps the Wizard is actually a hedge mage, carefully tending his garden in solitude and communing with natural spirits instead of actively researching in a library, locked in a tower.

Acting stealthy, picking locks, and thievery aren't specific to a Rogue. Rogues simply specialize in such tasks. Plenty of warriors enter a battle rage, Barbarians have simply learned how to channel that rage to make themselves stronger during battle.

Decide what it takes to be a Druid within your setting, and discuss this with the player

Unfortunately, it seems you've allowed the player to assume the character class without fully discussing your setting and/or their backstory, and hence their role within your world. How did they gain their powers? Are they part of a Druidic order (By the book, they are in a Circle)? Are there repercussions from this order when a Druid acts out of interest?

Maybe the character isn't a druid at all?

One thing I should make explicit is the option that perhaps the character isn't a druid in your setting at all. After you discuss Druidism within your setting with the player, discuss other flavour-based options that allow him to keep the class but still take his character in another direction. From an example in the comments maybe the PC is from a barbarian tribe that uses nature-based magic (but to survive in nature rather than protect it). There are many explanations, as many as you can imagine, as to why your Player's character would have these powers without actually being a druid within the setting; mechanically a Druid, but not referred to as such by the other characters who inhabit your world.

There are some options available if you decide he's a druid in both name and function

After you discuss with the player how druids work in your setting, explain to them why, if his behaviour continues as it is, he will face certain consequences. Importantly, though, don't punish the player for his current "misdeeds," especially if you haven't already spoken. If, after you've had a discussion, the player continues behaviour disruptive to the natural world, make a story out of it.

• Perhaps their Cirlce becomes determined to hunt him. Either to bring him to justice and remove his powers, or to hunt and kill him like one would a mad animal.

• Maybe the god(s) or spirits of the natural world disapprove of their actions and deem them unworthy of their druidity and remove their powers until they repents. I certainly know certain Fey may have a problem with their behaviour.

• Maybe their magics start to go wrong, and the animals and plants he calls to his aid turn on him instead of acting as allies?

• Perhaps an investigation by the local guardsmen has led them to believe the PC is responsible for a recent robbery?

By the book, you can take inspiration from other rules on how to act

My one suggestion would be to treat it as a Paladin who has broken his oath. A short blurb on this may be found on pg.86 of the PHB, and there is an Oathbreaker Paladin in the DMG. Suggest the character play a fallen druid (if they can exist in your setting) and find/create an such a class with them if they find this method interesting.

In the end, it is your Player's Character

Perhaps suggest the player take class levels in either Barbarian or Rogue, as they may better fit their current playstyle, but do not force them to do so. There's nothing in the rules dictating their behaviour, and it seems to me they were not aware of your expectations.

But do take the opportunity to inspire yourself and your campaign and present challenges for the player and their party. All actions have consequences.