That's my take, that words (any words) are all about how you use them. If I were to call another poster a [censored] head, that would be inappropreate, no matter what the word was. If it was dumb head, it would not be ok, because its impolite to say to another person, even though the words are mild. But in a piece of fiction, if a cherictor would want to say what ever they wanted to say, then that would be just dandy, because the offended party (if any) would be a fictional creation of my own design, and their sense of being offended or not would be in my own hands.
But, I understand that some words hold more sensability than others, and there are people who don't want to hear that in any context, and I can respect that desire, even if I don't share it.
And I expect the mods will take all these considerations to heart, and look more kindly on a word in a fictional bit that slips out, and less kindly at a rant at another player.