The ones radicalizing these people are responsible for squeezing them out of public debate. What if these people were going around insisting the Earth is flat, trying to force other people to agree with you, then increasingly lashing out when others don't agree? Oh, and they are picking up new adherents by doing this as well.

Consistent enforcement of the rules (which Apple is not good at, I will say) would have avoided this becoming such a problem. Parler has been a cesspit for its whole existence, as far as I know, and approximately nobody would have cared if Apple never let them on the App Store. And fewer people would blindly believe that the earth is flat.