For me, it's all about how people approach those kinds of topics. I love debate so long as both sides come to the table with reasonable, fact-based evidence to support their side. When it breaks down into anecdotes or reiteration of propaganda-sounding hyperbole, I shy away and would rather avoid the topic. I love to be wrong so long as I can also be right.
That said, there are certainly some kinds of ideas or views that inform you quite a lot about another person right from the get-go. Not believing in evolution or global warming are indefensible in this day and age, so I'm somewhat closed-minded when dealing with such people. They're typically too far to another extreme for there to be any fruitful conversation about things with me and I'd be just as likely to harden them in their beliefs as I would provide an alternative.
It's all about specific issues, though. Labels like "Democrat" and "Republican" are misleading. I'm not against guns, demand gay marriage, love regulations, not always a fan of unions, hate corporate person-hood, etc. I have friends who disagree on all of those issues, but they're still people with whom I can have a meaningful interaction.