Why should they? Freedom of association is key Western principle. Steam chose not to associate with them anymore. If the user don't like it they should have sued them in court instead.

If I report my employer for an OSHA violation and they retaliate that's illegal. Of course such laws hardly ever stopped anyone so it's a very bad idea to depend on it but the principle is certainly there.

Being able to freely threaten reprisal against people exercising their rights circumvents those rights.

Freedom of association applies to individuals; it's a non-sequiter here.