In that case, this hinges on whether websites having the right to moderate themselves as they see fit does indeed have negative externalities on society - and, even if so, whether those negative externalities outweigh the harm of dictating how websites moderate themselves. Perhaps we differently value the rights to speech, press, and association - all of which such a regulation fundamentally infringes.

Notice that I ain't mentioning corporations or individuals here, because that piece fundamentally does not matter; an individual could create a website used by billions, and a corporation could create a website used by a single person (not to mention that there are countless organizational structures beyond just corporations - especially once you go beyond the constraint of what's legally recognized). What matters is the size of the audience, and "you have such and such rights unless you're popular enough to have any tangible influence on society at which point the State will dictate what you're allowed to say or not say" doesn't sit well with me.