I think these two things are not mutually exclusive.

There are people who should not (but unfortunately do) engage with harmful ideas online.

The best case scenario is these people shout into the void, and nobody takes them seriously.

More often than not, these people lack the epistemology to engage in civil disagreement.

The worst case scenario is these people vindicate the bigots through weak arguments, meltdowns, and fallacies, which get screenshot / clipped / shared to other bigots.

This isn't an argument for suggesting people should shut up; I would like for people to be better trained in critical thinking. That's not always possible though, and some people need to step off the highway.