My favorite fantasy in this genre is imagining what I could say to a kid that would make him think he should substitute his own judgment for mine. My fantasy argument goes like this:Kid: Can I climb on the roof?
Me: No. You'd get hurt.
Kid: I'll be careful. And my friend Brian climbs on his roof all the time. He never falls off.
Now at this point you realize that regular reasoning isn't going to win the day. You have to resort to the "Because I said so" fall-back, but while effective, that never seems like a clean win to me. To the kid it appears you don't have a good reason and you're just being an ass about it. That's why I fantasize about the rest of the discussion going this way:
Me: Do you know who invented the roof?
Me: It wasn't a kid. In fact, nothing important has ever been invented by a kid. Do you know why that is?
Kid: I don't care.
Me: It's because your brain won't be fully developed until sometime in your twenties.
Kid: I'm not listening TRA-LA-LA-LA-LA!!!
Me: You don't understand why you can't go on the roof because your brain isn't developed enough to understand the risk involved.
Kid: You suck. I hate you.
Me: I'll make you a deal. If you can find anything in this house that was invented by a kid, I'll admit that kids know as much as adults and you can climb on the roof. Use my computer, which incidentally was invented by adults. Go nuts.
(seven hours later)
Kid: Golly. Not only was I wrong, but probably stupid as well, and perhaps a little bit insane. I now adopt your viewpoint as my own. Would you like a bite of my sandwich?
Me: Thanks, but the last time you washed your hands was in amniotic fluid.