RE: "Would it be freedom of speech for them to show a full-frontal teaser for Penthouse TV in the middle of "Rudolph's Hunky-Dory Christmas" in prime time too?"
Absolutely. I firmly believe that the open marketplace should be the ONLY "regulatory body" for television. The FCC is a big government/socialist threat to freedom of speech which is allowed to operate by even the most conservative elected officials because it allows them an easy cash cow for federal funds and an easy fundamentalist scapegoat on which to pin public attention when it should be on more pressing matters (like the WOT and tax reform).
I'm sure the rage of America's parents, coupled with the requisite sponsor boycotts and letterwriting campaigns would be more than enough to ensure that such a (yes, diisgusting) hypothetical situation like the one you presented would never occur again on a major network.
NOTE: Although this in no way changes my opinion on this matter, I must raise an objection to your straw-man comparison of something as wild and tasteless as hardcore porn to something as mild as Degrassi High, which boasts nothing worse than the positive (actually just non-critical) portrayal of a homosexual character.
By your ugly words-- repeated by a shamefully large number here on FR-- I take it you have never had a friend who happened to be gay, or maybe you have never even met a gay man. Whether or not you approve of their behavior (and in America, we ALL are entitled to our various opinions on this subject) I don't think they mean you any harm.