To answer the question, let's connect the dots in the rulebook.
On YS203 the following quote is found:
Stress is a transitory thing, but sometimes conflicts will have
lasting effects on a character— serious injuries, embarrassments,
phobias, and the like. These effects are collectively called
consequences, and they are a special kind of aspect.
The emphasis on aspect is mine- put in to show that a consequence is an aspect. This is not the only place that a consequence is referred to as an aspect, either, so it is intentional, i.e. on YS204 the following quote is found:
Also keep in mind that, because a consequence is an aspect, it can be
tagged, invoked, and compelled like any other aspect. Opponents with
fate points will take advantage of this, because invoking a
consequence to help win a fight is very easy to justify. Further, the
attacker that inflicted the consequence gets one tag on it (which he
may give to an ally), just like aspects placed by a maneuver.
With that in mind, we go back to the standard rules for compelling an aspect, i.e. on YS98:
Compel: Either receive a fate point when one of your character’s
aspects works to his disadvantage, or spend a fate point to avoid that
disadvantage.
One other thing to note with Consequences as Aspects: All the rules for aspects apply, so if appropriate, you can invoke one of your own consequences for a positive effect, something which people sometimes miss.
Consider it a self-compel
Although concession does give you greater control over your fate, you're still losing--and you're choosing to lose when you still have a chance of winning.
you can interrupt any action at any time before the roll is made to declare that you concede the conflict. (Fate Core 167)
That means if the dice are rolled and you're taken out, you can't call backsies. If you're not taken out yet, it's possible to still win.
By conceding, you're forfeiting the chance to win, and that's pretty much a self-compel. And you get extra points for the consequences you got in the conflict as if each one had been compelled, because "[y]ou can think of this as a compel of each aspect taken in the conflict[....] [T]he assumption is that those consequences directly contributed to the character’s defeat." (DFRPG Your Story 206)
Consider it a drama bribe
The idea driving Fate storytelling is that every time something happens to complicate your life, you get game currency which you can spend to make your life easier later. Fate Core is very up-front about the fact that the Fate point economy drives this cycle of crisis and victory.
Conceding is still losing, and you should always negotiate a concession until it has a dramatic bite to it, like any other compel. Concession Fate points are a way of encouraging crisis while simultaneously providing the tools for future victory--again, just like any other compel or invocation. It's the way the engine powers the story.
It means your villain can usually escape to plot another day
NPCs can concede too! And should, often, if they're smart and have a sense of self-preservation. It gives the players a sense of accomplishment (because they achieved whatever goal they had when they entered the conflict) but sets up the villain as canny and positioned to wreak more havoc because of his fistful of Fate points.
Consider it an opportunity for the GM to do less work
Hey, my player's gonna tell me how he gets shafted instead of my having to come up with it. Awesome. I'll throw him a couple FP in appreciation.
Why do you want to discourage concession?
Concession is a pretty shiny mechanic, and although Fate is very flexible about many things, discouraging players from being able to cash in their cards when they walked into too much trouble is going to make them more cautious than the "proactive, dramatic, competent" characters Fate wants to tell stories about.
Allowing concessions is a frontline weapon in the war against ten-foot pole paranoia and the boring, time-wasting practices that come with such paranoia.
Come on into chat when you have the rep and we'll talk about what your underlying goals and motives are for discouraging concession. Probably we can work out some other way to satisfy your motives.
Best Answer
I'm going to dodge the main question, because it's a situation that shouldn't come up. Here's why:
The situation you've outlined there involves at least two compels, not one. The first compel is the one already mentioned, which results in the transformation if the player accepts. The second compel, which you've skipped in the example, is compelling Ravenous and Bloodthirsty Wolf to say that "the Werewolf is so hungry that it would turn on its teammates...". When that compel happens, the player has already earned a Fate point from accepting the compel on Curse of the Lycanthrope and can easily refuse this new compel, which is what they actually want to do.
By skipping right to the effect of an Aspect "by consensus", you're hamstringing the player's ability to interact with the relevant mechanics, and you get a weird situation where they immediately want to concede the fight. The solution is to not skip that compel, and so give the player the option to avoid the fight in more mechanically-clean manner.
"But," you say, "doesn't the consensus matter?" Yes, it does, but even if everyone agrees that an Aspect should have a certain result, you're still obligated to pay for the compel. Compels that players suggest and agree to are not free! No matter who suggests a compel on an Aspect, the player whose character Aspect it is still gets a Fate point. Asking for compels on an Aspect is a major way that players can influence the narrative in Fate, and can happen even when nobody uses the word "compel."