I've tried passive-aggressively just believing they were wrong. Funny. Nothing happened.
It isn't like "passive-aggressively just believing they were wrong" and "direct confrontation and calling them stupid" are the only tactics available.
You're a gamer, right? So, think creatively. You have a monster in front of you - but it is too big to just do a frontal assault. And walking away means it keeps the treasure. What do you do? You find a way to trick it, or go around it, right?
You have people who have a heartfelt belief that is resistant to simple statements of fact. Just getting in their faces with facts and trying to insult/shame them doesn't work.
So, you approach them with fewer facts, less "You are wrongity-wrong!", less personal accusation, but more emotionally gripping human impact. Or, you just realize the adults are a lost cause, and go for the youth who don't yet have the biases engaged.