In the past, when "private property" was literally property, a whole town owned by a company (used to be very common), American courts decided that the company owning the town couldn't restrict free speech in that town.
These days the "property" in question is just a fancy telecom system. And it's already an established principle in America that the phone company doesn't cut off your line just because you're talking some political smack.
These days the "property" in question is just a fancy telecom system. And it's already an established principle in America that the phone company doesn't cut off your line just because you're talking some political smack.