> I don't even understand why Youtube should be forced by a country to host someone's content.
It doesn't appear to be settled even in U.S. law whether requiring a company to host something would be governmental overreach. The traditional "common carrier" doctrine is pretty broad. It's not an exact analogy for the kind of regulation some people would like governments to undertake regarding YouTube, Twitter, Facebook, etc., but it's not totally unrelated either.
Eugene Volokh from UCLA's law school recently posted a 79-page draft article on the legalities of regulating social media companies as common carriers under U.S. federal law: https://www2.law.ucla.edu/volokh/carrier.pdf. One large section, II.A., "The General Constitutionality of Compelled Hosting" (pp. 35-58), argues that compelled hosting isn't in general prohibited by the U.S. federal constitution, so in his view the U.S. Congress could pass a common-carrier-style law mandating such companies host content on a neutral basis, if they wanted to (at least if the law avoids various issues he identifies).