What the hell does "no offense" mean?

In my experience, people say “no offense” when they know their words will probably offend. Somehow, the “no offense” is supposed to indicate that even though the words are offensive, no offense is meant. What’s the deal with that?

If words are offensive, it seems to me, then they are offensive whether you say “no offense” or not. You can’t just get off so easily. You are trying to remove responsibility for your words, so the other person can’t take offense, at least not openly, if they do take offense.

Ok, so this is a rant. It just annoys the hell out of me. My daughter says it all the time. I just saw someone write it in an answer here. I just think it’s mean, and that if you do not want to offend, you shouldn’t say what you think, and try to pass it off as an inoffensive comment. And if you feel it necessary to make an offensive comment, you should “man up” and take responsibility for it.

No offense.