First of all, there's a massive difference between transporting a private package from point A to point B vs hosting someone's speech on a privately owned platform and broadcasting that speech through a privately owned network, with wider consequences that do not come into play when dealing with private correspondences between parties.
Next, paying a fee to a private company to ship your package confers certain obligations about what you are entitled to, when you are utilizing a privately owned platform for free, you are not entitled to anything.
Finally, a private company is certainly within their rights to refuse to ship your package based on an any legal criteria they choose.
First of all, there's a massive difference between transporting a private package from point A to point B vs hosting someone's speech on a privately owned platform and broadcasting that speech through a privately owned network, with wider consequences that do not come into play when dealing with private correspondences between parties.
Next, paying a fee to a private company to ship your package confers certain obligations about what you are entitled to, when you are utilizing a privately owned platform for free, you are not entitled to anything.
Finally, a private company is certainly within their rights to refuse to ship your package based on an any legal criteria they choose.