I thought car tags had to be turned back in?
Depends on the state.
Here's an excerpt from a letter the state of Washington's Department of Licensing sent to the license plate's seller, explaining why it was unsafe at any speed:
The Department of Licensing has received several complaints regarding your license plate FDUBYA. The personalized license plate committee reviewed all the documentation and decided to cancel your plate because the message is offensive to good taste and decency.