Ok, it's time to get off Rumsfeld's back about the prisoner abuse thing. Though it's true the abuse is scandalous, there is nothing about it that suggests Donald Rumsfeld should resign.
In the case of soldiers committing war crimes, in any army, there is always a desire to find out who is responsible and punish them. That's ok. We have a history of searching out such people and doing bad things to them. We discourage war crimes as a matter of policy. So, who are the bad guys here?
Naturally, the ones who did the actual abusing are bad guys. They may try to do the Nuremberg Shuffle ("I was just following orders." "If I didn't do it somebody else would.") but U.S. soldiers are instructed early about how to handle an illegal order. They have procedures for refusing to follow what they believe is an illegal order and should be able to deal competently. The soldiers responsible have no one to blame but themselves.
Then there is the matter of their leader. The officer directly over a group of soldiers is responsible for the actions of that group. Even if she or he can't stop the group from doing something wrong, an officer should still know what is happening and make an effort to deal with the situation. Again, there are policies for such circumstances. This means that the immediate leader of these soldiers is accountable.
Should the next leader up the chain of command be held accountable? If that leader knew or ordered the activity, then he or she should definitely be taken to task. If the person directly beneath them kept the activities suitably hidden, our higher leader should be embarrassed but not hanged.
That's the way it goes, on up the chain of command. Unless someone higher up has issued an order that contravenes existing policy, we must assume that he or she is still ordering our normal behavior and that the crime is out of his or her hands. That goes all the way up to the Secretary of Defense and the President.
Should Donald Rumsfeld resign? Not over this. Unless it can be shown that he ordered or knew of the ordering of abuse, there is no way he can be held accountable for these activities.
Why do some want his resignation anyway? The usual political reasons. If you have reasons why you think Rumsfeld should go, deal with those reasons rather than using a tragedy for petty political sniping. Otherwise, you're abusing the political system as badly as the soldiers abused those prisoners.