No private company is considered required to promote or protect free speech. Each forum is able to say "don't like our policies, then go somewhere else".
This even seems quite reasonable. Why should any particular forum be forced to allow any particular kind of speech? Should Facebook be forced to allow porn as something that is protected by freedom of expression?
On the flip side, as more and more of meaningful speech occurs on these not-really-public forums of Twitter, Facebook, and Reddit, there exists quite a bit of unease on my part for these global companies to insist on narrowing expression on these platforms to that which they deem acceptable by whatever internal process they desire.
Facebook's study that showed they could manipulate people's feelings by altering the feed algorithm indicates this is an awful lot of power handed to a company focused on making profits and staying on the good side of governmental organizations.
YouTube recently started changing their policies that has started to create problems for people using their platforms.
This would likely be okay if there were real public space on the web, but it currently operates more as a series of visits to other people's private property. The release valve is a persons ability to create their own corner of the internet, but even this must leap through various ISP and web host providers terms of service. Additionally, is it really speech if you're just doing the internet equivalent of talking to yourself on an island in the middle of nowhere?
Cases like this photo will only become more apparent as time goes on. I'm not sure how society will negotiate these ideas, but at present, the commercial interests are leading the conversation in their favor.