I used to commute with a group of folks from Facebook, Oracle, and Amazon, and none of them seemed to have any moral qualms about their employers. My buddy from Oracle invited me to apply to work on his team, and in explaining why I couldn't consider working at Oracle, I mentioned some recent terrible thing Oracle had done in the open source community. His response was that Amazon contributed even less open source (which I believe is true). So I think in the end, the internal justification is "Yeah, maybe I'm contributing to something immoral, but it's less immoral than X & Y".