Create a set of rules, hold people to them, and enforce them fairly and impartially. Bans and defederation should not be for people whose opinions you don’t like - it should be reserved for people who cannot communicate in any meaningful / respectful way. Spammers, and trolls basically.
Which is why the easiest thing to do is just have the discussions. If someone wants to act as if they’re just a regular person bringing up crime statistics about black people or something, just engage in good faith and present your counter. If they’re genuine, you’ve provided a genuine response, if they’re not, you’re still winning because their goal is to either prove you can’t ask certain questions or that people are hiding from the truth. Also, you automatically get an opportunity to influence any 3rd parties simply reading the exchange.