You are not alone in this. For my wife and I it's not politics it's religion. Your insight into the rudeness and how it kind of sneaks in is probably the most significant avenue to defeating this issue. It takes a conversation. Both people have to agree to talk to the other in a way that they're not pushing boundaries they don't push with other people in their lives. For my wife and I this means I can't really talk to her about my beliefs because it just upsets her. But we love each other a lot, so yes heated stuff happens with people who have fundamentally different beliefs but still love each other. It's just figuring out a way to be civil to each other and respecting each other's boundaries that will get you through. It's tough. But really if you're a passionate person like I am you're going to find things you disagree with people on no matter who your mate is.