He’s insecure, and seeks attention, and approval. The mature thing to do would be to find someone else to hang with, or help the guy out by telling him that you recognize that he is at the very least, exaggerating the truth. And that it’s not necessary for him to do that, in order to get your approval. He needs to find something that makes him more confident, that he’s a good person. Best way to do that, is to volunteer to help someone else. It’s impossible to help someone else, without helping yourself.