I try make friends with people that have different opinions than me because it helps me understand their point of view on issues. The more I can understand and issue, the easier it is to intermediate opposite views. Being understanding is one of the most underrated things you can do in a friendship.
I guess there is a limit of understanding and when such people try to shove utter bull**** down your throat then it's not really understanding anymore. You can try and listen and talk all you want but a lot of times people are just stubborn and won't listen to you anyway.