You might get better answers from others here who've gone through this situation before, but personally when it comes time for that I'm not going to try to refute anything they say. You don't need to prove anything to them, and the only thing that will come of it is more preaching and possibly a JC. Instead, I would go with something like "Right now I'm leaving things in Jehovah's hands. I've prayed about my situation and I have confidence that Jehovah understands why I do what I do since he is the only one who can read my heart condition."
Thank them for their time and concern and assure them that you'll let them know as soon as there's anything that they can help you with. That puts the ball in your court, and you're probably not planning on hitting it back.