I think this is actually a fundamental problem with not having downvotes. Tribalist things that would normally get half upvotes and half downvotes now just get upvotes. It's the same thing with the iphone/android stories. With downvotes, we'd be reading a lot fewer of them.
But downvotes just as often (or more often, I'd argue) create exactly the tribalism you describe. Restrict users to only a positive input mechanism and you'll drastically reduce bullying and other gang behavior.
I guess if one camp is clearly more popular than the other then it will win out all the time, instead of both winning out all the time.
I guess I don't see this being a problem "all the time" the way you do. Sure, every so often you start seeing lots of articles about the same contentious debate happening in a pretty tight echo chamber (or sometimes you start seeing nothing but Erlang articles at PG's behest), but save for the occasional dud most of what rises to the top around here seems pretty well worth my time.
Just flag the article. When it reaches some threshold, the story gets kicked.