Few people who are doing things that will, with a high degree of certainty, result in harm to others for their own profit want others to be publicly pointing those things out.
Painting this as "trash-talking Amazon", however the fired workers' words are phrased, is hugely disingenuous. We're not talking about someone going out there and saying, "Man, Amazon is just such a loser! They're so ugly, their mama dropped them when they were born and wouldn't pick them up!"
Amazon is putting their workers' lives and health in danger, knowingly and deliberately, for their own profit. Anyone who is truthfully bringing the details of this to the public is a whistleblower, and needs to be considered as such and granted the full protection of the law.
Like...you know legality and morality are not the same thing, right?