An article by Seymour Hersh in this week's New Yorker makes it clear that the military engaged in a massive cover-up regarding higher-level involvement in and knowledge about the torture at Abu Ghraib and elsewhere. By higher-up, I mean it's clear to the forcibly retired General Taguba that Bush and Rumsfeld were likely involved in ordering torture, deliberately ignoring the evidence that their wishes were being all too fully carried out, and then squelching the investigation so that it would only reach the low-level grunts.
I've said it before in this blog. We often hear about torture as a means, as in the ticking time-bomb scenario. But to these people, torture is the end, not a means to some other end.
Why? Mainly just to establish that they can, because if you can do this then you can do anything.
Any other reasons? Well, one might ask why Bush as a tweener or adolescent dynamited frogs, as he apparently did. The child is father of the man.