Short of telling them "religion is evil and worthy of ridicule and you should not accept it in your presence" or actively encouraging them to adopt antisocial behaviors I don't see how this works.

Lemmy is an astoundingly hateful place.

"Religious" covers an extremely wide area of behavior. There are lots of good religious people and shitty non-religious people. Need to be more specific.

Better to be friendly than judging someone based on their parents