I agree that there's plenty of room for improvement but I wouldn't say that most of the downvoted comments I see are just “contrarian legitimate and respectful views” — usually the ones I see heavily downloaded are also things like standard issue talking points repeated with no additional contribution and/or especially those containing falsehoods or material omissions.
I have seen some oddly flagged posts which I tend to assume are people going through someone's history in reaction to a different thread.
Re: the Facebook effect, some subjects are definitely heated but I tend to see that tracking how genuine someone sounds — it seems like people do okay if they, for example, are talking about how Facebook is helpful for communities they're part of and don't sound like they're doing pro bono PR. One challenge I think certain topics get is that they've been rehashed enough that a lot of people are quick with the downvotes if a comment opens with something which sounds predictable so there is definitely something be said for making sure that the initial opening doesn't sound cliched.
There are some users who were banned because the repeatedly broke the guidelines but continue to post, and that they got banned doesn't mean that all their comments are bad, just too many of them.
