I felt awkward and I left my friend in the living room all by himself.
Why did you feel awkward about leaving him alone like that?
I heard bad things about him, he's an asshole
I'm sorry you had to hear those opinions about him, and it's fine for you to bail if you're not comfortable. But eventually, you'd have to tell him why there is such an air about him. You don't want him to always feel like something wrong is going on.
Probably not. I don't care about his feelings. It's not my problem.
If he is your friend you should tell him how you feel. It is normal to leave a situation if it makes you feel uneasy. Not letting him know anything will not allow him to change.