I know you said that you wanted opinions on "general limits" when it comes to friendships, but I have to say in regards to your situation I would ABSOLUTLEY back out of that friendship. I mean, that's my own personal opinion you know?

A person's choices and beliefs are absolutely their rights, but I draw the line when it affects me personally and it hurts my heart. In my opinion, the fact that what that friend said about being a homophobic white supremicist made you feel like puking is a good indicator of how you feel about being friends with him. What I am saying is, since you feel so STRONGLY about this issue, it will keep coming up and bugging the crap outta you if you continue a freindship with him. Like it will always be that nagging thought in the back of your mind festering as you communicate with him, you follow me?

Hope that helps my friend, good luck!