Powell is a prime example of the military mind set that puts the chain of command and dedication to the service above everything else. And like several other military guys (not to mention some dedicated public servents from other branches of the government), he learned the hard way that under the Bush administration loyalty is a one way street and they are more concerned with their politcal advantage then the services being able to do their jobs.
But you are right, the idea that Powell is some pristine political outsider is wrong. It is an example of the common but misguided and very dangerous belief that the military is beyond politics. Pentagon politics are rather different then other politics, and better concealed from the public at large. But there is just as much there as anywhere.
Jay