1. Even if the First Amendment is only limited to the government, the concept of free speech predates and extends far beyond the First Amendment.

2. Does the Constitution apply if the government allows private entities to take over roles of the government? There is the concept of utilities and common carriers that extend upon this logic.

3. Even without the above points, one should still be able to see a double standard being applied to violent/extremist speech. Saying a company can do whatever it wants doesn't explain what the company actually wants. If the company is applying a double standard to what speech it allows, then the true wants of the company is something we need to discuss and decide do we want to tolerate.