That said, as someone who has ran online businesses, I still don't agree with you that it's some universal principal that businesses should be held to. I've dealt with trolls of the same ilk as Milo Yiannopoulos, and you know what? When I think about how things went, it would have sucked up a hell of a lot less resources and time of myself, the business, and my other customers if I had simply censored them immediately.
I'm saying that free speech is more than a law.
Perhaps you're referring to the first amendment, but I'm making the point that you can't limit this discussion to the first amendment.
And businesses should be held to universal principles, above and beyond the law. We should demand businesses' decisions be ethical, not simply legal.
The concept of freedom of speech is that pure speech is free from government-imposed consequences, but that private parties can and do choose what expressed ideas to support, oppose, reward, and punish. That's the fundamental concept of the marketplace of ideas.
The idea of freedom of speech is not that speech should be free of all consequences.
Now because businesses (especially those that are creations of government, like any that operate as juridical entities distinct from the constituent natural persons) are creatures of government and/or often depend on exercise of government powers, there is an argument for limiting the consequences that they can impose for speech in certain cases, especially when they are in monopolistic roles, and even more especially when that is in regard to key communications media, because those are in effect acts of government by other means.