When people see something they don't like, they don't think, "Well, any even-handed system will put up things I don't like sometimes." They think: Bias! Outrage! And some rush to "J'accuse!". In any large group this will happen to quite a few people every day (sometimes the same few!), and it takes 100x as much effort to responsibly respond to the j'accuses as to fire them off in the first place. This would amount to a DoS attack on resources that we could otherwise use to make HN better.
Therefore our goal should not be the impossible one of placating everybody with a litigious bee in their bonnet, but (a) being able to say "no, we don't do that" in good conscience, and (b) retaining the good will of the community as a whole. Actually we like to help users with bees in their bonnets too, but to think it can always be done leads to madness.
We're toying with adding vouch links so users can vouch for a story they don't think should be marked as a flamewar. That's something that might improve the quality of HN.