> Downvotes will happen regardless of how well reasoned your argument is
Some will, but its very rare that I've seen posts retain a net of negative moderation when they contribute substantially, regardless of the side of an issue they are on (though I've seen controversial-but-substantial comments quickly get heavily downvoted before recovering.)
And I've seen this on every side of issues -- often to opposing posts in the same discussion -- so I don't think its an "echo-chamber" effect, but more that certain topics bringout more kneejerk negative responses from people on either side.
(Its funny that, in regard to accusations of HN being an echo chamber or hivemind, I've seen various posters proclaim with confidence that it was -- and that that hivemind was, variously, liberal, leftist, libertarian, capitalist, pro-corporate, anti-corporate, and in support or opposition to various companies, and any of a number of other things. I think people are way to quick to equate some people disagreeing with or downvoting their posts to HN being a hivemind biased against them.)