Gopher,
I hesitate at giving advice - but if they could physically cope with it, I would not go easy.
I would make it clear to my parents (in verbal word) that I loved God, and that they serve men - that you are in not the slightest doubt.
And emphatical that you know the wtbts' to be just miserable mess of men who have applied spiritual teachings to flesh, and that you won't have anything to do with such a darkness of intellect, not now, not ever. And refuse your reply as to how or why you know. AND, make sure he well understands that it is HIS responsibility that he has delivered his family into the hands of men, not yours.
NO RETREAT in your verbal stand whatsoever - you both love God and reject his org. - no anger, no heatedness, just resolute assurance. Explain that if he wants to serve men then that's his choice - as he's an adult - but it's ridiculously unreasonable to expect you to do such a thing, knowing that they are simply a sham of charletons - that it is not you who are disturbed by the speak of men - that you are a man.
Personally I'd chew them right out.
paduan