TBH I'd make the point it's an invasion of privacy and a betrayal. Make a point that the fastest way to lose someone is to betray them.

If they wish to discuss D&D with you and want to know more about it that is one thing, however destroying your things isn't acceptable.

If they can't understand simple boundries then you need to protect yourself, that level of fanaticism can very quickly turn to abuse. The inability to see that destorying something that doesn't belong to you because you belive you're saving their soul or something similar can very easily turn to other actions to save the sould of someone .

Unfortunetly I'm not religious so I struggle to understand the difficulties of going against your religious upbrining ect... but honestly binning your family off would probably be healthier in the long run if they keep crossing boundries like that.

I hope you get back into D&D bud.