Worse Than "Happy Holidays"

When did it become acceptable to say "butt" in polite society, when not referring to a cut of meat? When I was a kid, "butt" was one of those "awww, you said. . . ." words that would get you tattled on, and people went out of their way to use, ahem, softer words, such as: tush, behind, bottom, buns, derriere, seat. When aerobics first came in, instructors said "glutes" to avoid using the b-word. I was once in a class where we were told to sit very upright on our "sit bones." Now there's an ad for the new video from the lady who did "Buns of Steel;" It's called "I Want That B---!" Does anyone else remember that once we weren't allowed to say that word?
I realize that of all the vulgarities in common use today, that's an extremely mild one, but in my youth so much was made of not saying it that it sounds extremely vulgar in my ears. In fact many words that are probably technically worse don't bother me nearly as much. So, anyway, if anyone wants to take up a language crusade, I'd rather kill "butt" than "Happy Holidays."