Sooo, I'm having some struggles right now. The dumb part is it has nothing to do with me, but my emotions are still reeling.

Today, my best friend told me that he slept with his neighbor (they live in a duplex). Except, the neighbor is and has been in a relationship for two years. And she lives with her boyfriend. And the girlfriend is actually completely dependent on her boyfriend because she doesn't have a job. And my friend knows the boyfriend. And my friend kept giving bs excuses for why this was okay -- one of which really pissed me off. First he said it was okay because she has "mental problems" because apparently "mental problems" mean cheating doesn't really count (don't worry, I yelled at him for that one). He also said it was okay because she was hot; he wouldn't have done anything with her if she had been ugly.

He refuses to ask her to break up with her boyfriend because "he's good for her" and my friend doesn't want to be the reason they break up.

Basically, I'm having a really hard time dealing with this. He's my best friend, but he's doing something that really upsets me. I'm so disappointed, but I don't know if I'm more disappointed that he did it or that he doesn't seem to care that he did it, that he would do it again (apparently they both want to). He basically said that he doesn't feel bad about this at all because if the girl's boyfriend is too dumb to realize his girlfriend is taking advantage of him and not being faithful, then it's his own fault he's with her.

I'm just so.. flabbergasted. I'm angry at him. I can't believe him. He isn't the person I met and became best friends with. When we first met, he never would have done this, he refused to be friends with people that smoked pot, he rarely drank. Now he smokes and drinks to oblivion and sleeps with any girl that will have him. I know why he's doing this, he's desperate for love and affection and is taking this because he feels if he doesn't get it from her, he won't get it from anyone. But it's just horrifying to see what he's doing to feel wanted, to boost his extremely low self esteem. I mentioned that I missed the guy I met when we first started being friends. He said, "I kind of don't. I have more fun as the new me."

Baaah... how do I stop being so upset about all this?? This doesn't affect me, but I can't let it go. I don't want to stop being friends with him, I just want him to stop being this person I don't want to be around.

Thanks for reading, everyone. Sorry if I got long; just really frustrated and needed to vent and get some outside opinions to tell me to stop stressing over something that has no impact on my life.