I see plenty of conservative types having civilized debates with liberals here, and again, just because a comment gets low-rated (often for good reason, but often not as well), that doesn't mean it's deleted and the person banned. It's still there, available to be read.
Also, don't forget, it doesn't take many downvotes to get a comment hidden, and both sides have a few people with several alts that they use just to solo downvote-to-hidden people that they disagree with.