70% of the Trump’s statements on the campaign trail were false aka “fake news”.
http://www.politico.com/magazine/story/2017/01/donald-trump-lies-liar-effect-brain-214658

Trump’s favorite source of media news was Breitbart.
https://www.buzzfeed.com/charliewarzel/trumps-information-universe?utm_term=.qoxLNMB7A#.kfmygrOon

Therefore Breitbart is the leading source of “Fake news”.

The FCC can fine media for “fake news” as done here.
https://www.freepress.net/press-release/2011/3/25/fcc-fines-local-tv-stations-airing-fake-news

Therefore, Breitbart should be fined.