Genuine political dissent would become logistically impossible, and virtual mob rule a certainty.
There's a major difference between political dissent and hate speech.
You can say: "I don't think transgender people should be allowed to choose which bathroom they go to", that just makes you a shitty person with no compassion. But if you say "If I see a trans women in the mens bathroom I'll beat them up out of there", that is very clearly hate speech and threats of violence.
It's not like it's hard to treat people with basic respect. You can disagree without resorting to hateful comments and threats and name calling. If you don't see the hate speech problem you're probably part of the problem because surprise, it's only conservatives you see online constantly spewing FUD and hate speech.