Spice channel??? You see more on MTV everyday and PG-13 movies, then you saw at the Superbowl.
You are assuming that people who watched the halftime show are USED to watching MTV.
THE POINT is, that display was totally inappropriate for the audience. Period. People who want to see this kind of thing can choose to do so. Aren't libertines always saying to those who object, "Well, if you don't like it, change the channel."?
Most parents assume they can watch a sporting event without being subjected to trashy sexually explicit displays by no-talent "celebrities". It doesn't take a great deal of talent or imagination to take your clothes off in public. Only a below average IQ.