That's only half true. Even in a country with strong worker protection laws such as Germany you can get fired for a lot more things than just poor performance. Damaging your employer's reputation can actually be part of it. I don't know enough about the laws to be able to determine whether this would get you in trouble over here, but I certainly would be very cautious doing something like that. I even read that the US has better whistleblowing protection than much of Europe.
It's however true that you can't fire without cause and that courts usually demand strong evidence for such cause. So people would be more likely to sue.
That said, I still find Amazon's behaviour totally shameful, legal or not.