The FCC is well enabled to make judgment calls. Yes a network can bring that judgement call in front of an actual judge in a court of law. That doesn't mean the FCC lacks the authority for such calls, only that the judge likely has higher authority.

Do you have an example of the FCC enforcing action against a television broadcaster or personality for saying something materially similar to what Kimmel said, at the same time slot and same genre of programming, on the basis that it was false and/or defamatory, without any sort of pre-existing court case related to the same?