It depends on what the contract says. Each side has various clauses to protect their interests, like say if Kimmel starting showing porn on his show, now the station risks FCC license they can drop him. I imagine there was something.
Technically I think they could have fought, could have argued he was just describing the behavior of maga people or that his shows is all made up parody and everyone should know it, etc. However it would have been a losing PR battle even if the FCC lost eventually in court.
