Not trusting the government, the courts, the mainstream media, etc. is baked into their belief system. It carries zero weight with them to say that a court convicted someone.

As Jonathan Swift said: "Reasoning will never make a Man correct an ill Opinion, which by Reasoning he never acquired", or in more modern language, you can't change someone's mind using reason, if they didn't get there using reason in the first place.

IMO, the only thing that will change people is if it stops being a social identity they can cling to and feel proud of, and instead becomes one that's a source of shame and loneliness. It might not really change their minds, but it might make them be less vocal about it. And, maybe eventually, they'll find a new group they can feel part of, but hopefully one with less awful, destructive beliefs.