Well, one example would be threatening people either directly or through violent public messaging. These are antisocial behaviors. Of the 10,000 words any human reads on any day, removing unnecessary negativity is an absolute virtue. This is the same reason we have spam filters. Would you consider Google to be censoring your email inbox? Wanting to force every human to see every other human's toxic dialogue is an invocation of Hanlon's Razor.

Not an American issue by the way, if your country happens to vote this is happening in your elections too.