Why, it's the work of the Wonderful Magical Commerce Clause. It breathes life into the Constitution!
It's not that hard to understand. The radio frequency sector of the electromagnetic spectrum is a limited natural resource somewhat like navigable waterways and airspace. It is also a commercially valuble commodity that crosses state lines, which places it within the realm of interstate commerce. The Constitution grants congress the right to regulate interstate commerce, therefore congress has authority to regulate what are called the "airwaves" in popular vernacular.
In 1932 (I believe) congress placed the publicly owned airwaves under the supervision of the newly created Federal Communications Commission. The FCC was given authority to license specified slices of the radio frequency spectrum to individual commercial, private, and public service users. It also bears the responsibilty of determining what is in the best interest of the public regarding the use the various licensees make of their slice of the spectrum, and also has authority to impose rules and regulations and enforce those rules and regulations by fines and/or revocation of licenses.
IMHO, over the course of the last two or three decades the FCC has to a considerable degree gradually abdicated its assigned responsibilty to police the publicly owned airwaves and enforce rules and regulations that were intended to benefit the general public which corporately owns those airwaves. Hopefully the recent furor over the Superbowl halftime fiasco has awakened the public to the problem and made it aware that it's watchdog has been napping.
But I'm not holding my breath while I wait for the watchdog to be awakened by an aroused public. The culture war that has raged since the Woodstock generation arrived on the scene is in full swing, and the good guys have been on the losing end of the fight for most of the war. The same sector of the public which was outraged by the display on publicly owned property of a stone tablet inscribed with ten laws, which incidentally are the models for many of the basic laws of most civilized nations, is the same sector which doesn't see any irony in it's demand that unscrupulous broadcasters be allowed to use publicly owned airwaves to slake it's insatiable thirst for pornography and salacious "humor". As I mentioned before, the good guys have been on the losing side of the culture war almost from it's beginning, and I don't hold out much hope for the tide of battle to turn in our favor anytime soon.
In the meantime, our children are being taught in an oblique but effective manner that illicit sex and illegal drugs are merely recreational pastimes and subjects of humorous anecdotes, and that no harm can result from their use. What an awful way to utilize a publicly owned asset.