The Constitution restricts government from taking certain actions, but private property owners exist under no such restrictions.
Consider as an analogy the First Amendment. Every citizen has the right to protest a particular politician. But not on my property - should they attempt a political protest they'll be asked to leave, and eventially removed should they refuse. Their Constitutionally-guaranteed right to free speech does not exist once they enter my property. This is no different.
Why should we defend companies that are knowingly using property rights as an excuse to violate Second Amendment rights?
We are all obligated to support & defend the US Constitution, even CEO's.
jones