Butt Rock
Butt Rock is really irony.  In simple terms it is any music that one does not like and/or lives in denial that they actually listened to that music during that time period but now want to pretend they did not.  It has actually nothing to do with quality of said music just the arrogance, inflated ego, and heavy pride of the one labeling it butt rock so they can distance themselves and feel superior.

The sad truth is that those who label it butt rock may as well had been those that listened to it at the time and thus are calling themselves butt rockers.  Hence the irony.
Butt Rock? Art #5 knows he listened to that music back in the 80s.  He is not fooling anyone.  He knows he was a butt rocker then.