Sinclair has a government-granted monopoly on the frequencies on which they broadcast. Google and Facebook offer service accessible over the (almost entirely) capacity-unconstrained Internet medium.
And a movie theatre has a government granted monopoly on a piece of land on which they show movies. Doesn't mean you can't just build another one next door.
Facebook has an actual monolopy on an entire market.
I agree that Facebook is a bigger issue, but you can't just build on more frequency. There's only a small, already claimed amount, that is suitable and allowed for broadcasting tv
