There is no right or wrong age for curse words, the only reason why you're told to not use them when you're young is so that you don't get in a habit of using them just because "it's cool." Though technically curse words aren't even really cool, they're just ways to weaken vocabulary and strengthen ignorance. So in that case instead of teaching my child curse words, I would examplify to him the strength of verbosity in one's vocabulary, and the joy of having one clueless as to what one is saying.
Some of you may call me crazy, or weird for saying that, but I say it's genius if you stump someone.
It's just a good way to put yourself above others levels in a non immature way.