I would argue that in this day and age the corporate Internet Gatekeepers (i.e. Google, Facebook, Twitter, Verizon, AT&T, Comcast etc.) have more leverage to threaten free speech and thought on a global scale than any government or organization has in history.
Sure, it's legal, but we all know just because something is legal doesn't mean it should be.
Humanity can't survive and evolve without freedom of thought. That is what's important here.
I agree with you that major corporations can threaten free speech more than governments, but my point is: when a government censorship's something is different when a corporation censors something, because when the gov. makes the decision, you have nowhere to run.
It seems like we have little to nowhere to run in both cases. Sure we can always "pick another service" to use, but it will invariably be another corporately owned service in which the number one concern is making money above all else, to the detriment of free thought.
Sure, it's legal, but we all know just because something is legal doesn't mean it should be.
Humanity can't survive and evolve without freedom of thought. That is what's important here.