When it comes to the law, there are no fair or unfair tax laws. They are just tax laws. Putting the word fair or unfair in front of the word law is purely subjective. I'm not defending Amazon either way, all I am saying is that they are operating within the boundaries set out by the law.
As outsiders, we can both comment on what we deem to fair or unfair - but at the end of the day, we are all bound by those same rules.