You're confusing free speech with the American first amendment.
Free speech is an universal principle, probably best expressed in the Universal Declaration of Human Rights (which the US signed):
> Everyone has the right to freedom of opinion and expression; this right includes freedom to hold opinions without interference and to seek, receive and impart information and ideas through any media and regardless of frontiers.
I didn't know about this, actually. Nice! I mean that's as clear-cut as it can get, although media might mean format rather than platform, otherwise all moderation is technically a breach of this right: though I suppose if it's in the terms and conditions then all parties must agree to the use of moderation for specific cases.
Free speech is an universal principle, probably best expressed in the Universal Declaration of Human Rights (which the US signed):
> Everyone has the right to freedom of opinion and expression; this right includes freedom to hold opinions without interference and to seek, receive and impart information and ideas through any media and regardless of frontiers.
Notice the part I emphasized.