Democratic input and regulatory oversight over discourse is in the same category as total surveillance: a perfectly benevolent operator would certainly be able to produce a better world with it, but we cannot trust anyone with that kind of power.
Just because there would be some democratic input doesn't mean there would be total democratic control. I think that's a pretty un-substantiated slippery slope.
Similar issues appear for the internet with respect to backbone capacity and video streaming, but political speech mostly doesn't encounter the kinds of scarcity problems that justify such a heavy hand.