[RPG] How to handle the party that doesn’t trust you

Yes. You should leave.

These people are not respectful, and are not worth your time. Tell your brother you're not interested, and stop joining the call — he's the only person you have actual contact with, and given the behaviour of the rest of the group you're best cutting ties with them completely. (Who would want friends like that?)

You could expend effort working with them to overcome their talking over you, their negligence of you getting value from the game, and their aggressive and disrespectful behaviour toward you and making you feel uncomfortable — but that's a lot of effort, not likely to succeed with this group, and not really worth it when there's a world of gaming groups out there full of people who are quite ready to treat you and others respectfully like anyone ought to. (The fact they're making rape jokes in front of a rape victim is appalling, and one of several strong signs they're probably not interested in engaging with you constructively on resolving any of this. Indeed, a lot of what you've described reads to me as abuse.)

We have some guidance available on finding other groups that you might find useful, kindly gathered by a resident moderator:

• Where can I find other RPG players? for finding (or creating) a group to play with in real life.
• Finding online RPG players for a play-by-chat RPG Campaign? for the same online via chat.
• How do I find a friendly, inclusive roleplay group online? specifically concerns finding an accepting group as a queer individual — you may or may not identify as that or find that effort necessary to accommodate yourself in a group.

Bad match with a gaming group, how to leave? provides general advice for politely leaving groups, but in this circumstance, you don't need to use it. The group does not need, and won't be receptive to, an exit conversation. (Your brother may be different in this regard, but you'll need to judge that for yourself.) Other people in the future may be receptive.

You mentioned these people were in the furry fandom — I'll advise based on personal experience that this behaviour is completely non-representative of that fandom, and exceptionally awful and heinous bullying by any standard, including theirs. Individuals in the furry subculture may be somewhat more inclined to poorer social mores than many groups, but the subculture is largely made up of harmless, well-intentioned, friendly individuals.

Roleplaying games should always be fun. If you're not having fun, talk and work with your group to resolve the source of un-fun, or leave and find another one. You found this one, you can find another.

(NB: In a previous version of this answer I'd unwittingly given some advice that appeared to suggest this behaviour was normal for people in the furry fandom. It isn't. At all. It's awful, and entirely outside any behavioural standard of the subculture.)

The way I understand it

Your problem player rejects your concerns when you try to address behaviours that the whole group agree are problematic and would also be problematic for the problem player if one of his players had the same behaviours in the game he masters?

Seems to me like he is asking people to tolerate a behaviour he would not tolerate from others. IMO he should meet you halfway instead of rejecting your arguments, but he's not.

Discussion did not work. More discussion might?

So trying to talk with him doesn't work and it sounds to me like it does not work because this player is being very childish, transforming his group's valid concerns into something they are not, i.e. personal attacks.

He also seems to have a double standard when it comes to how he behaves.

I personally can be very firm while also being very diplomatic. Honestly, someone who would twist my arguments into personal attacks and try to turn himself into a martyr would get an earful from me about the fact that we are discussing valid concerns and the fact he's acting like... let's say a child.

It would be a very serious discussion about how I do not appreciate his being childish, and if he keeps proving to me than he cannot be civil and respectful during our exchanges, I would totally lose any kind of interest I have in interacting with him.

When a problem player does not want to even start considering that his behaviour might be problematic, when diplomacy fails, there are not many options left: endure, leave or kick him out? Different people/groups have different thresholds for that, but that's an immutable fact of life: once you hit the "point of no return", then your options are very limited.

Trying to deal with the "my guy syndrome"

"My guy would do this" is not automatically a logical or valid argument that answers every situation. This argument can always be debated!

When one of my players uses this "excuse" without further explanation, I probe them further for an explanation, for deeper insight into their character's psyche.

A simple way to do it is to ask him, "But why would your character be/think/act this way?". Ask questions but do not "say stuff about his character" like "He would not be smart/dumb enough to do that", since that would be crossing a line where you start telling him how he should play his character.

Challenge him on his excuses. Like in the instance of the barbarian deciding to invade a whole outpost by himself, when he clearly has no way to win and will clearly end up "badly" for his character, I would have asked him, "Is your barbarian smart or tactical enough to realize he has no chances? Or does he have a death wish?".

Of course, that's really not foolproof because it is a more passive approach and still depends on the problem player's reactions/decisions...

...which brings me to my next point.

If "my guy would do this" is okay for him, then it is okay for other players.

Never forget that you are a group of people. Usually, permissions given to a player are implicitly given to other players... else, you have an unfair group and this will lead to frictions/frustrations for some.

So if the logic of "my guy would do that, there's nothing you can do about it" is valid for him, it is also valid for you.

For instance, I once had to deal with a problem player who was a bit similar to yours: strong-headed, constantly shifting arguments to turn a debate about the game into something personal between players. He was also passive-aggressive in how he showed his discontent at the table and was very stubborn that everything he did would be possible (even though that never was our argument; we were very clear that possible does not mean believable or desirable).

His favorite argument was, you guessed it, the "my guy would do that, it totally makes sense" line that he would give to us constantly. Frustrations were building to the point we decided we needed to have a talk about it... which did not work. Basically all we got from him was "you guys want to control my character", when what we really were trying to make him realize was that "Our characters did try to influence him, in-game, which is something our characters would do and makes total sense... but since it did not work we now have to have this discussion out of character".

I used all the tricks, showed him parts of the DMG which tackle group interactions and how it is important for the group to establish clear guidelines for what we're looking for, etc, to no avail.

When the discussion got heated between him and the GM, I suggested that we stop it there. I asked the problem player to think about what we said while stressing that this is nothing personal and is only about "managing the game" and I said "hope to see you all next week".

The next week we had a full table (surprisingly), but the problem player kept being problematic. He did more in-game shenanigans which impacted the whole group and derailed the game, once again, when he actually tried to sneak into the King's Chamber during the night we were spending at the Castle to try and steal the King's spellbook. He got caught and thrown in prison, and our group had to undergo a "trial". We succeeded in convincing the King that the thief was acting alone, and the GM salvaged the situation by having the King "punish us" by sending us on a quest.

But here's when the problematic "my guy syndrome" also became a solution: When the King asked us if we needed the thief for this quest, my character acted according to his own beliefs and personality and said, "No, let him rot in jail and hopefully let this be a lesson for him for when we get back". I have to specify we knew the quest would be done in less than 1 session, so I thought this was a brilliant way to have our problem player get a taste of his own medicine.

When he got frustrated at the table saying that it would be very boring for him to just watch us play for 3 hours and that I was being a bitch, I calmly told him about "those many times where we had to watch him for more than an hour because of his PC's shenanigans and the fact that if my action would cause 3-4 hours of boredom for him, his actions in the past caused at least 10 hours of boredom for me and all others around the table, minimum". I was polite but firm, and when he kept complaining I told him, "that's enough, I don't want to have this debate with you, especially if you are gonna be childish about it". And that was it. He sulked; we played.

But I believe that made him realize that we had just as many ways to influence the game and his character as he did, and that we just had chosen not to do so before, but that we would start enforcing consequences for his character's dumb moves in-character.

TL;DR: Your characters do not have to rescue the barbarian the next time he derails a mission. Maybe your group will start thinking they are better off without him... and that's totally legit. It is an in-character reaction to a fellow comrade's actions and is totally legit and even uses the main argument of the problem player against him, in-game.