And the commentaries answer, "because they enjoyed it." They weren't just following orders, they were reveling in them. Sir Richard Burton (the explorer type) said that the desire of a slave is not to be free, but to have his own slave. Even if we believed carrying out inhumane orders was acceptable, (which I don't), it is certainly unacceptable to delight in their execution. And that's why the response must be swift and severe. In a time of war, brutality may be necessary, even desirable, but the joy in other's suffering can't be permitted to gain accendency in the heart or mind. I see the joy in them, and I find it utterly repulsive.
[Brian: Well cook on me then!]