Why? The media companies have always done so. The press is and always was "patricians" of printing press discourse. You can't say whatever you like on a news paper. The TV companies and Cable companies are and always were "patricians" of tv programming. You can't say whatever you like on a tv program. The publishing companies are and always were "patricians" of the books. You can't say whatever you like on a book and get them to print it, promote it and distribute if they disagree. Radio companies are and always were "patricians" of the radio waves, you need a license to operate a radio and they decide what gets on air.

Why the double standard?

Now, you can say whatever you like on the internet, you just are not entitle to force other people and companies to give you a platform to do so. Facebook, Youtube, this site, etc., doesn't owe you sh#t. If you want to publish something that they don't like, host it and promote it yourself, just as if you want to put something in the news that they don't like, or on TV or on the radio or on a book.

The insane and childish authoritarianism of the author of this article that believes that "Mail Chimp" doesn't tell him what to do with their service but instead he is the one that tells them how to run their private for profit company is both comical and sad. If you don't like the terms of service, stop using their service. That's how that works. If you think that they are infringing on your rights, them take them to court, don't click bait about it.