Doc, what you suggest would not be technically possible, all avatars from the gravatar site are presented to this site in the same way, there would be no way to ban one certain avatar and leave others as OK.
Bernie, I would have thought it's fairly obvious that the avatar you posted is not acceptable, although I wasn't in the slightest bit offended by it either (I thought it was quite funny too) it's was obvious what would happen when the ed spotted it (as both myself and craft pointed out)