The only thing you should ever say to someone telling you an uncorroborated bigoted conspiracy theory is: “What did you do to those kids? You know what I’m talking about. We all know.”, and refuse to change the subject.

No one whose world is built on hearsay and anecdote will ever acknowledge a debunking; they’ll just double down on their “secret knowledge” and insist you’re “falling for the coverup”. The only viable game is to put them on the other side of their own fallacy.