I have always allowed my kids to curse with one exception - not in public and not in our home when younger guests are over. Ironically, my kids very seldom curse, while the kids who curse the most are those from ostensibly religious families who punish their kids for cursing.

I didn't need to read JS to know exactly where the phrase "sucks" came from.

"I would be much quicker to jump on my kid for saying an unkind thing," says Pekkanen, "even if he used perfect language to do so."
Exactly. The not forbidden, but strongly discouraged word in our house is "stupid." 'Use it sparingly and only when you mean it - and never towards anyone in this house.'