The UX designer probably work in a cushy Amazon corporate office with free snacks and drinks, but amazon warehouse roles are probably under more spartan and strict conditions. How does Amazon warehouse work conditions compare to other warehouse work conditions. That's the better comparable.
If any programmer was thrown into a construction or blue collar work environment they probably won't like the work conditions. But for cost reasons they can't extend the same benefits for people who sort packages the same as people who write code or design screens.
The best way to protest an employer is to not work for them. As UX designers who made it into Amazon they probably have other choices.