Earlier quoted context omitted.
You're being downvoted for expressing a contrarian viewpoint. This kind of censorship isn't even targeting hate speech, and it drives me crazy. Why downvote them?
Because he's criticizing liberals and most people on HN are liberals. Most censorship ("hate speech" included) is code for shutting your political opponents up. HN makes this really easy by making comments hard to read by removing contrast with the background as they get voted down; post something too much against the grain and it'll get flagged and hidden by default. When you hand users the power to shut those with…
I think it's ok to use the up and down arrows to express agreement. Obviously the uparrows aren't only for applauding politeness, so it seems reasonable that the downarrows aren't only for booing rudeness.
It only becomes abuse when people resort to karma bombing: downvoting a lot of comments by one user without reading them in order to subtract maximum karma. Fortunately we now have several levels of software to protect against that.