I already regret the last paragraph. Let's just say that I agree that it's good to be a polite, reasonable person. I just am not so sure that hard-fast rules such as "it's never ok to be rude" are reasonable. I see the matter such: there is a palette of expressions, and every one of these may have its uses.
To skillfully use this palette is completely another matter: it's horribly crude to use wrong kind of expression, and doesn't reflect well on the speaker. Communication is, after all, a process where you need to make yourself understood to another. Whether I just transgressed remains to be seen...