I think the detail that this is an LGBT safe space group is a really important one.

Normally this is just a conflict between the nb player's patience vs the older player's speed to adapt, with you stuck as the one who has to decide what to do if the nb player loses patience.

That's still all this is really, but that fact that this is an lgbt group means you should probably side with the nb player if it comes to it. If you join a group like that, I think respecting pronouns is assumed. The older player is the one violating the expectations. It's great that everyone has patience for him to improve (genuinely great, as it's the best chance he has to learn and making him feel accepted among people he isn't usually around is a really nice thing to

Imagine if instead this was advertised as a christian safe space and one player kept saying "god damn it" on bad rolls.