I often have this debate with my fiance. As a child, if I had used the word "hell" or "damn", I would have been slapped into the following month.
I am a pretty liberal guy in a lot of respects. However, when it comes to children and morals, I'm old fashioned because I was raised that way. I think that anyone under the age of at least 14 that uses anything stronger than "Dang" or "Cooties" needs a good beating. Ok, maybe that's a little too strong.
How would you react to a six year old standing in the store yelling "Mommy I want that damn toy or you can go to hell!" instead of "Mommy, mommy, please get me that toy, please get it for me"
Ok, so they both sound like brats.

However, I think I'd be a little shocked hearing that first one. Do you agree? If not, then you may not realize it but you already agree that they're bad words. If, on the other hand, you think it's ok for a six year old to talk like that, well, no comment.