To put it plainly, Rumsfeld treats people like crap. Working for him is like working for Leona Helmsley, except that Leona is less self-centered. Unless you are one of his sycophants, equipped with a good set of knee-pads and plenty of lip balm, you can expect to be booted down the stairs on a regular basis.
Truth be told, some senior officers deserve to be treated that way, because that is how they always treated their subordinates. But Rummy does not discriminate between perfumed princes and the real thinkers and leaders. He has driven more than one of the latter to hang up his hat in disgust, to his service's and the nation's loss.
Gosh! Think Rummy's, uh, demands might have affected how WMD intelligence made its way up the chain of command?