He promoted 2020 election denial conspiracies. Moves to mess with due process for voting, or to disrupt the peaceful transfer of power (say, promoting coup attempts) are some of the gravest threats to peace possible in a democracy, as far as speech goes. Lying about such, is right up there.
[edit] sources easily searchable if you have the topics, letting people pick their own works better if search turns them up pretty easily, that way there’s no worry that I’m choosing clips out of context or something.