It's not like this is me giving a lecture - it's more like a conversation. Like any conversation topics drift. But maybe to give an example, If I say "I don't think homosexuality is wrong according to the bible" then the response is usually either "why? What about..." or "you are wrong." If it's something like the first - great we can have a conversation about this! If it's the second, I say "we'll maybe you're right" then depending on the context either shrug it off or justify my position with a short sentence such as "Romans chapter 1 is ambiguous." That allows the other person to discuss or not discuss the topic as far as they are comfortable with it without hurting the friendship.
No, I think that friendships with people who believe differently from me are valuable. For me, I view a persons beliefs as a result of upbringing and culture plus biological tendencies. If I isolate myself from "bigots" not only do I lose access to people who might actually be right (albeit partially) I also lose the ability to help change their views. EDIT - in my personal story, people who took the time to befriend me in spite of my bigoted beliefs changed my values, albeit after many years....