> If a private developer were to take over most residential areas in a section of town

There is a finite amount of land in a town, so a monopoly can exclude people. This is not true of video hosting - there can be as many video hosts as people care to build, and they are all equally usable from anywhere on the internet.

> Since YouTube has a monopoly on video content on the internet

They don't.

Now, if ISPs started censoring particular political viewpoints, that would be different IMO. It's much harder to get a different ISP (at least where I live) than it is to browse to a different web site.