If a company banned me from saying x, I can in theory go to another platform and say the same thing. Failing that, I can build my own site. There are a handful of things I can do to say x. Failing a digital platform, I can always go out on the street and say it. The police won't stop me.
If a government does the same, they have the power to prevent me from saying such a thing on all platforms, but worse, I can't even go out on the streets to say it, because I can get arrested. I could face maximum prison times, or worse, in some countries I could face the death penalty.
There is a huge difference.