Yeah, I remember when I got fed up with that. Basically everyone else in my family got into politics. They were all on the same side, too, so if I disagreed with anything or sounded like I disagreed with anything, I got an earful. It got to the point where I stopped looking into political issues and stopped forming opinions about current events.
Heck, every time the news came on, members of my family would start yelling about it. It wasn't the best mix for me, so I grew to resent that kind of behavior.
Still, it's not all bad. Because of that I've made friends with people who are highly religious where I am not, and I even have nice conversations with Jehova's witnesses when they come by (as opposed to people who normally send them away. XP). That's not to say I automatically agree with everything someone says. If I do disagree with something, I just say "Actually I don't agree with that." and try to explain to the best of my ability why. Keeping a level head in those situations is something important to me personally. I've seen my siblings raise their voices automatically when they disagree from being so involved. It's not pretty.
Basically, it's fine to disagree with friends. Of course I could go on and on and on about this, but I'll stop now. XP