The "badness" of some words provides them an important semiotic power. Someone who curses all the time flouts a cultural norm. That is valuable information to strangers. If all cultural norms were material - e.g., a taboo on unprovoked physical violence - harm would need to be done before a person's character could be assessed. But, thanks to wholly arbitrary taboos such as that against "bad" words, people can signal their grasp of, or attitude toward, community values without doing any real harm.

Then, having created bad words, we can use them in extreme situations, or for shock or humor, in circumstances where their use does not imply anything about the user's general commitment to norms. The words are just sitting there; we should use them when appropriate. Otherwise, they stop being bad words and become obsolete words.