I'm sorry you're going through this. Right now, your son in law is brainwashed. There is nothing you can do about that. NOTHING. Maybe he'll change his thinking at some point. Maybe not. In the meantime, you don't need to be exposed to a destructive person.

You've done the right thing. I don't know if you'll be able to continue to have a relationship with your daughter, but right now, this is the right thing to do for your own peace of mind.