But if all that is true then the solution isn't even more government regulation and control which if they were enforcing their idea of the 1st amendment on them is exactly what you would get. The solution is to eliminate those financial ties and influence. In other words, end efforts like In-Q-Tel. But regardless, just because the government put up some of the venture capital, doesn't mean they created something. Nor does it mean they should have control of it unless you are saying they are the majority stakeholder and own most of the stock. I do not believe that to be true though.
If I start a company, make the company public (i.e. sell stock) and then the government decides to buy some of that stock (possibly covertly), then they should have control over my company and be able to tell me that I can't decide who publishes on my platform? If it turns out the government has stock in a newspaper company or publishing company then that means anyone then has the right to publish there? That's giving the government an awful lot of power.
I don't see how on earth you could call facebook or youtube monopolies. There are plenty of alternatives, one of which we are using right now. They also compete with other media entities around the world.