I really dislike the term "bad words"
Oh, so bad! They are just words and it depends how you use them, so the words aren't "bad" all the time. Just my random opinion on something irrelevant.
As for the thread, we just do, whether it be out of anger, sadness, jealously, whatever. Sometime it's mistakes, sometimes it's not. We're people. I don't like insults. I like joke insults as in insulting someone as a joke (Works must with friends), but not insults that are meant to harm. I've insulted people before and I dislike it unless they deserve it. As for those I've insulted and I honestly regret/didn't mean it, I tell them I'm sorry, but what's said was said. And sort of going against what I said earlier, maybe we do mean it afterall, like deep down, but we don't want to ever say it something. Who knows?
Anyways, yeah, we're humans, not perfect, and therefore insults are born. Some do it for fun, some do it for the sake of being mean, some do it out of sadness, etc....Just how the world rolls.