The First Amendment does not extend to corporations. It's a U.S. government thing. Companies can shut speech down all they want. But the thing is this is destructive. This is discriminatory. And what they're telling themselves is they're making a much more peaceful environment. "We are creating a much more conducive and productive and peaceful environment," when they're not. They're suppressing opinion. They are inflicting their own world view and demanding that it be agreed with and acceded to. And if it's not, you get fired.