> Isn't that why the NC-17 rating was created in the first place - to avoid the stigma of hard-core porn that had attached itself to X?

Yeah, but the mistake was in replacing X at all. A new rating at the top end of the scale comes into being exactly when the old one is booted out? Obviously people were going to figure it was simply a replacement, a new name for the same stuff. What they should have done is kept the X and ranked it above the new NC-17. This mirrors the way the rest of the modern world's rating systems work.