the much better "joke" was when Harley got up on stage and started putting ON her costume to beckon a disloyal mob boss in order to strip him out of his skin. That took way much more creativity than the rape.
Motto. And I found the skinning much more shocking than the rape, not only because it (or at least the result) was shown explicitly, but because it's (AFAIK) a rare plot occurrence in mainstream comics. Shooting, knifing, gassing, weird-ray-zapping, bone-breaking--all common, as are rape and child molestation, although the latter two obviously are never shown explicitly. Skinning, not so much. (There was an Alan Moore Swamp Thing story which had a gruesome panel of a man's partially-skinned face. But that's all I can think of offhand.)