Warren sent an official letter, not just her personal opinion. That certainly implies using her governmental authority to suppress free speech.
I’d think it’s a form of prior restraint, since she wants Amazon to modify the search algorithm so that this book does not come up in the list of publications on the subject.
I get that, and too that most people are intimidated by these liars, because these liars can and do abuse their power in ways that cause physical and mental distress.
I don't believe there is any remedy at law. Sure, there may be harsh words, and breaches of "ethics" and "rules."
At any rate, might as well have fake government to go along with fake news.