While it is true that facts and logic don’t change people's mind, that’s not to say that nothing will change people’s mind.
Social proof and arguments from authority often persuade people to reevaluate their position.
So the most effective things to say to JWs may include: JW growth has slowed down dramatically in recent years and many are leaving the organisation after finding information online. Or, the royal commission in Australia found that JWs are very poor at protecting children. In fact they found over a thousand cases of abuse and not a single one was reported to the police.