The FCC isn't really the radio police. Broadcasting in the United States is a very unique public-private partnership. The stations are private businesses that are licensed to use public airwaves. The FCC has rules and regulations that govern how those private businesses can use the airwaves. But those rules are pretty loose and open to interpretation.
But a lot of it is up to the public. If you feel a particular station isn't fit to hold a license, it's your duty to challenge that license, or complain to the FCC Complaints Division. They don't have the staff to drive around the country and monitor every station. The license renewal process is pretty open, and if you feel a station should not be renewed, you can file a petition online. If no petitions are received, the license will likely be renewed almost as easily as your own driver's license. There isn't much difference between operating a vehicle on the public highways and operating a radio station on the airwaves. It's in the best interest of the government to keep as many stations on the air as possible, regardless of what they program. So they're not interested in making the job of broadcasting more difficult than it already is. Very similar to other regulatory agencies, like Food & Drug or Alcohol, Tobacco & Firearms.