But it's copyright laws that allowed this to happen legally. How should Amazon decide which legal rights publishers get to keep and which rights they don't? And are corporations the right entity to decide what is moral and what isn't? Would you blame chain manufacturers for slavery, or the laws which make slavery legal?
This whole thing goes to show how DRM can negatively effect a consumer
But DRM is just the mechanism for enforcing what people perceive as immoral laws. If books were removed once-bought in a way without DRM, surely people wouldn't be any less outraged, would they?