I shop at both Wal-Mart and Amazon, oddly both also benefit some smaller companies I purchase from. Wal-Mart shopping centers, at least near me, have all sorts of restaurants and specialty stores I like/use/need. Amazon's market place has let me source some products that were previously difficult to find elsewhere (Skyflakes crackers for one, many other items from that side of the world could be found but not consistently or for good pricing)
The book industry needs to change, I haven't come up against the dark side of Amazon's influence. I did watch for years when Apple and the publishers clearly broke the law and cheered when they got caught as I had seen prices for books I bought just sky rocket.
As for how their employees are treated or their "perceived" treatment, local employment laws cover those. Avoiding unionization is not a crime and should not be held against anyone. Much of retail outside of grocery is not unionized. When the same unions hire no benefit, no union, temps to protest tell me again how they are the good guys?