You're neglecting the market effects of networks that make these 'private' businesses de facto monopolies when you make your comparison to private ownership.

We have so little precedent with these society shaping forms of communication and content, it would seem very strange to me if we had already arrived at an optimum when it comes to how we should treat them. I don't necessarily have an answer to said predicament, but I definitely think 'do nothing and let unelected business decide how the conversation should end' is not a good answer.