Jerky half-friend dude? Help?

I don't know why some people act like that, but I'd avoid him. In the end, he'll be the one with the short end of the stick. Imagine all the friends, girlfriends, and other relationships that he has already and will continue to miss out on because of his attitude. Will he ever be in a serious relationship? Will he eventually want to marry and have children? Unfortunately for him, everyone changes. Even if he searches for what he considers to be the perfect person (on the outside), people change due to age, illness, accidents, etc.; and he cannot choose what his children will look like either. Even he himself will change with time. I fully believe there will come a day and a time when someone else will treat him the same way he is treating so many others.