I think you need to dig a bit more deeply into the motivation of some (though not all) of the generals who have come out so decisively against Rumsfeld's (and Bush's) prosecution of the war.
Rumsfeld took on the SecDef job with the eye towards totally revamping our armed forces, remodeling it from a large force with mainly conventional military tactics and doctrine capable of dealing with the similarly-disposed Soviet Union's armed forces to one dealing with smaller-scale conflicts and situations that demand rapid deployment.
As is typical when military leaders whose entire professional careers have been built on the status quo are challenged to think outside the box, some ressited the infringement on their turf by a civilian (for historical context, do some research on how General Billy Mitchell was treated when he was advocating the primacy of air power in the 1920s). Some chose to resign in protest of Rumsfeld's actions. Some chose to remain but try their best to obstruct Rumsfeld's proposed changes. And some embraced the new way of thinking and sought to improve it.
Much is made of what Gen. Shinseki says that criticizes the war effort. Little was made of the endorsement of the cause and the plan of Gen. Tommy Franks. I guess your judgement of who to pay attention to and who to ignore depends on your overall opinion of Rumsfeld and Bush.
"Liberals claim to want to give a hearing to other views, but then are shocked and offended to discover that there are other views."
William F. Buckley, Jr.