"Working them hard" might be an incitement to illegal treatment of prisoners, but it couldn't provide any kind of cover for the kind of stuff seen in some of those pictures.

Two things are often confused when the expression "obeying orders" is brought into play. One is where unwilling subordinates are coerced into acting in a criminal way by orders backed by sanctions. The other is where people take advantage of orders in order to behave in a criminal way. And you have situations where both processes are involved.

...........................

"any information gained through torture is most often useless" - generally speaking that's true, but the purpose of torture isn't just to collect information, it's also a way of supplying stuff that can be used as if it was information for internal purposes.

"Information" doesn't always need to be accurate to be useful. For example the stuff about WMDs was important in helping bring about the war, in spite of the fact that it was mostly total bullshit.