That is so funny! I deal with this crap all the time.
Here's what I do:
I'll ask my JW friend something like: "Hey, I'm having a problem and was hoping you could help me with it. Could you give me a reference from a secular source proving that Jerusalem fell in 607? Since it is a matter of history, and not just religious belief, I figure there's got to be something to substantiate the claim that 607 was the fall of Jerusalem. How did the WT arrive at that date?"
She comes back with about 200 pages of crap and websites that don't answer my questions at all. Then she wants me to ask MR. Knowitall JW. (No thanks.) Then she goes off on Christendom and how they are out to get the JWs, because they don't want Jehovah's kingdom spread, blah, blah, blah.......
"hmmm....Yeah, that's something to think about alright. But could you just answer my original question? Could you just give me ONE or TWO secular resources that support that the historic even of Jerusalem falling was in 607? Then I do the backward count down for her, show her how it isn't coming out to 607, ...."
Then she lets me know that I should be careful believing what the churches say, they're misleading me, I need to look into their history, yadda, yadda, yadda...........
"Gee, that's intersting. I'll have to do that. By the way, how about WT history? Got any good stuff about it? Surely you study lots about that! That might help me a bunch. Oh, and could you send me some historical secular proof supports the fall of Jerusalem happening in 607?"
I just counter the attack by staying on the original question.
You could do something similar: "Yeah, Dad. Maybe I am a fornicator. You haven't met any others in the the KH? Or going door-to-door? Even Jesus talked to fornicators, right? If a suspected fornicator at one of the doors you knock on asked you this same question, how would you answer them? I don't know what fornication has to do with my question. If you don't know the answer, just say so." Then repeat the question.