Best advice I can give you is to just stay away from them, don't even talk to the on the phone. Sounds like they are sucking all your good positive energy away from you, and that's not good. They are so brainwashed that they may never wake up from it, if they do they will seek you out for answers, that's when you can interact again slowly to make sure they are actually wanting answers.

Either stay away from them or let it all out on them. Just let loose and tell them they are wrong with all the facts and knowledge you've accumulated, and when your done speaking walk away. Hopefully you will shock them all into silence for you to have time to leave before they try to debate you. You will feel better for getting it all off your chest and walking away leaving them stunned is a bonus. And don't contact them again, let them contact you. If they have nothing nice to say hang up.

I'm sorry you have to deal with people like that, and to know that they are family is worse.