The right of free speech doesn't apply to a private company. A company has every right to dictate what services it will provide and the conditions for using those services. It is not a public communications carrier.
This is to conflate (as so often) the USA's legal/constitutional codes with the principle of free speech. That principle has to do with promoting criticism of ideas, and preventing the suppression of criticism. The US codes are (just) one instance of a way to support that principle. The principle applies to all criticism, and all suppression of criticism.