Is ATC communication subject to FCC profanity regulations?
I'm not sure if FCC broadcast regulations specifically apply to airband VHF: It's not really a "broadcast station" in the sense of FCC regulations, but rather a wireless service (RT) on spectrum delegated to another agency. The FAA handles regulation of the service, the FCC just gave them a particular chunk of the VHF spectrum to use for it.

Obscene or profane transmissions are generally frowned upon by both pilots and controllers though, and the FAA specifically prohibits "obscene, indecent,or profane language" on their communication services (JO 72103Z) - Controllers can face disciplinary action over it, and I imagine they could find something in the regulations to charge a pilot with if they wanted to.