but he's still trying to convince himself it was kind of hilarious.
That might be the most painful part of the story. He's your brother and you have an unresolved difference of opinion about what is appropriate behaviour (even while drinking) and what crosses the line. If he sobers up and sees/admits his contribution to the unpleasant situation, then you will be able to feel safe around him. If he does not see his contribution to the situation, you begin to disconnect from him. I suspect, though, that the disconnection began earlier and you had some idea of his behaviour. So, my question is this: Were you surprised at this or did you have some kind of clue from past incidents?
Tell Me A Story Of When Someone Was An Asshole
Here's my story of when someone was an asshole, since you asked: Am I an Ass?