The problem with this kind of consequentialist ethics is that thinking the end justifies the means generally makes you very vulnerable to manipulation by others who tell you what the ends will be and then ask you to do the means.
Remember, Guantanamo also had taxi drivers and aid workers in it. How many of them are you willing to torture in order to find the terrorist you've captured and maybe get some information that might help stop a future terrorist plot? The hypothetical of capturing a top general with a tight deadline provides a terrible intuition when it comes to torture.
But that is exactly the kind of intuition Rumsfeld et al wanted people to be thinking about, in order to justify torture^W enhanced interrogation techniques.