And also:

social networking sites are a private entity and have the right to make rules.

Of course they do. What they do not have the right is to act as if they were not hypocrites in the rules they make.

While keeping their right to make their own rules, they sure have no right to be hypocrites when they run into the wishes of governments and suddenly rediscover free-speech, free-enterprise and other nice libertarian propositions, whether it's because of Germany or Spain on data retention, or because of China and Syria on the falsehoods about their virtuous regimes, that their platforms help people publish.

And also, it's still better that they exist than that they don't. For all their shortcomings, including for instance just what I am criticizing, they contribute invaluably to flatten the public space and the organization of civil society.