My BF and I disagree on some things. He has much more of a militaristic "kill em all" attitude. Really our main disagreement is on the war, though he's slowly coming to my side. Muahahahaha

He does have insight I don't have though, since he fought over there for a couple years. However, that also has led to some prejudice on his part that I do not like to see or hear from him.
I couldn't be with a really religious person, because I just wouldn't be able to fully respect them I don't think. Not on the level I'd need to. And I'm sure they'd get sick of me rolling my eyes all the time.
I'm really not sure I could be with someone who had socialist or totalitarian views, either. Not if they were extreme. I could deal with someone who was anti-choice, but we'd just have to agree to never talk about it. I would end up getting far too upset with their desire to not allow me to control my own body, so again.. the respect thing would come into play.
I guess in short, it really depends just how extreme they are and on what issues. I'm in the middle, so I can tolerate some "leftness" and some "rightness".