It's impossible to deny freedom of speech (or freedom of association) to a company without denying those same freedoms to the people forming the company, or its customers or users of its service. That's one of the reasons companies do have freedom of speech, and exist as quasilegal "entities" in and of themselves. Rights don't cease to exist in aggregate.

Any legal pretense one could use to deny freedom of speech and expression to a company could also be used to deny any group - political parties, religions, specific races or genders, the press, etc.

Companies are groups of people. It's right there in the word "company".