Apart from the physical torture that they were submitted to, I believe the Jews were made to feel as if they weren't even human in the first place.
The phrase Arbeit macht frei, (which means Work sets you free), was often seen at the entrance of many concentration camps, and it summarizes the idea of having to be productive, in the way a machine would be, in order to one day prove to be worthy of the freedom that they were robbed of. I believe this would lead to feelings of despair, deep sadness, and anger towards their abusers, and the frustration of being unable to work more and more, as their health deteriorated progressively.
For me, a person's value goes beyond the material aspect of what they can produce. Even in today's context, people are way more than the money on their bank account or their possessions, they have an intrinsic value as a human being, with their own perspective of the world and principles on which they base their lives.
