What about the other part of their argument though? Do you really think censorship powers can be withheld from those who are eager to abuse them? If the incoming government in the US was constitutionally able to be sanctioning vigilante violence against racist speech, I'm pretty sure one of the first things they would do with that is to classify people protesting the Palestinian genocide as being valid targets, under the logic that criticizing Israel is racist, for example.

Even if it was true that censorship is a more effective way to control toxic rhetoric than honest discourse, it would still be the case that it is an incredibly dangerous weapon. If we can't ensure that untrustworthy malevolent people never get the power to use it, there's no way it does more good than harm.