A few years ago we were dealing with more straightforwardly sexualized pedophilia in underwear ads -- that was easy to compartmentalize and isolate off in the out-of-normal band. This is an attempt to normalize, to stay in band of normal behaviour.
As you suggest it may have been authored by a homosexual to promote pederasty by means of a female switcheroo -- which runs in the same vein as happened with Sex-in-the-City and Desperate Housewifes.
I think it more likely a South Park social cynic libertarian punching out at the hypocrisy in the MTV renditions of "Stacy's Mom" and subconsciously tuned into the same gesalt as the recent flurry of adult woman teachers hooking up with young boys.
Remember those Underoo commercials? How about those Calvin Klein commercials with the creepy men interviewing the boys in the basement?