Amazon is a state-supported monopoly (through a strange tax regime for internet business) that is quickly driving brick-and-mortar stores out of business. The fact that it uses this position to pressure publishers is anything but trivial.
They're using the same tax regime that's been in effect since the heyday of Sears, Roebuck (and yes, retailers whined about it then, too -- it even went to the Supreme Court).
Amazon pays sales taxes in every state where it has a physical presence. Just like every other business.
Do you think Random Penguin, Hachette, etc. pay taxes in your state? Unless you live in New York, no, they do not.
And a monopoly? There are many places where I can (and sometimes do) buy books other than Amazon.