I had the same questions from a close relative recently. I said exactly what Gnat suggested. That I know Jehovah loves me and he and his Son are the ones who do the judging, no one else. As to the 'Organisation' question, I just said that Jesus Christ is my Master, just as he said, we are to call no one on earth our leader.
Quote a well known and well used verse at them and they have no answers and they can't pin anything on you. It's hard not to get angry but it is really important to keep calm and think before you speak (something I'm trying to work on!) They are really good at turning the tables on you. Don't let them. Think out some 'blockers' beforehand that you can use just in case they have another go at you. If they say something that you have difficulty replying to without landing yourself in it, just stay silent.