Pretend they're in a cult. Partly because they are. And you just rescued someone from the cult, and you want to "deprogram" them. What are the techniques psychologists and therapists would use?

They would try to build a relationship, try to build trust. They wouldn't alienate or shame the individual. They'd take it slowly, and try to avoid outright denying their reality. Instead encouraging them to engage in questioning it.

Honestly most of it is just trying to be their friend. It's hard to stay in a cult and be friends with someone who isn't in it at the same time. Right now that's what the Conservative politicians are good at, is pretending to be their friends. You have to seem like the better friend.

See also, the black guy who has convinced a bunch of KKK members to quit: https://en.wikipedia.org/wiki/Daryl_Davis