We know de-platforming works because bigots fight against it so strongly. If de-platforming helped bigots, why do bigots oppose it?
Bigotry needs to be isolated and sidelined and given as little chance to be noticed as possible.
Bigots want attention by any means possible, because they know a certain percentage of the audience will agree with them. Don't give them an audience. Block them. Isolate them. Deny them any coverage.