NAH - I read this and actually sat on it for a while before responding. At first I was on your side OP, thinking that he should be happy that his parents just accepted him. But now I realize that even if your parents were there, ready to accept him, it may still have taken your brother a lot to build up the courage to come out. Even if his fears were based entirely in fantasy and everyone around him could see that your family would support him, he may have been filled with irrational fears that still made it difficult for him to come out.

I can understand why having it be so anticlimactic could make him feel resentful. Like he had to put all this work in to build up the courage and no one really cared. Granted, if he could have expressed that himself then people probably would have been much more willing to see his side of things, but it can be hard to reflect on your own feelings, especially when you're in the middle of them.

Granted this is all totally speculative, but I thought I might throw it out there as a possible explanation for his reaction.