Would now be a good time to remind savvy technical readers that it's crucial to have a solid grounding in ethics? It can be hard to draw a line when you work deep inside a system.
The reason why Amazon is likely anti union is not because of any "evil overloards" that believe that workers are slaves to be exploited, but the warehousing/shipping business runs on very narrow margins, and any restrictions in this regard means they stop being #1. This is simply an economic reason in a capitalist framework, not anything out of malice.
Based on the fact that they issued statements saying that people should petition government to raise the minimum wage, I think that if all the larger corporations were subject to unionization of workers, they would not have an issue with it. When everyone is on equal competitive ground, Amazon can win against the likes of WalMart and others.
Are you really trying to justify concerted effort to exploit people and rob people of basic rights and a decent living wage and work conditions because otherwise the richest company in the world might not have such a comfortable lead over the competition?