If you use that standard to judge what speech should be censored, then you need to censor just about everything. Perhaps starting with any talk about international relations because it might lead to war, and violent rap music, and criticism of people for their political views. Even yourself for suggesting that Voat users might start executing black people. What if that belief leads to violent retaliation by someone who reads it? That actually happened with Black Lives Matter - its ideas led at least one person to execute innocent policemen.

Before you judge something as morally right or wrong, you have to have a standard that you're judging it by. Otherwise you'll just end up making ad-hoc decisions that depend on your emotions at the moment with no particular meaning or direction. Your morals will wander aimlessly in the space of possible morals, pushed this way and that by peer pressure and the media. They'll also develop internal inconsistencies. What's the use of an aimless moral? You might as well just pick them randomly.

Yes, why it isn't?