From the second half of the sentence attributed to him: "I felt that [the President] ought to make the decision as to whether or not I stayed on."

He didn't just resign. He said, make an overt decision that you want me to stay. That gives him cover, which he now touts, and is essentially the opposite of an honorable resignation. (Perhaps this is a more common practice than I know.)

I've heard that the Japanese honor the "Captain of the Ship" doctrine to an extraordinary degree. A doctor once described to me an incident in which a neurosurgical patient was horribly disabled at an academic hospital. This led to the resignation of the Chairs of TWO departments, even though they clearly had no direct involvement in the error.

Rumsfeld could have done a great service to his country by resigning over the Abu Graib scandal, acknowledging that this was an intolerable error under his watch.