Look, it was not exactly a secret that they were plotting to kill Americans. He even admitted he was aware that plots were being hatched against America. He also knew of their attack against the Cole and he approved.
I doubt he knew anything more than what rat to eat, and what hand to wipe his ass with. I doubt Al-Queida would confide all their biggest secrets with an American malcontent.
Let's separate fact from fiction.
As far as Isreal and France being "friendly" and that makes it OK...Walker joined the Afghan army/taliban when there was no state of war. What happens if we turn on France or Isreal? Do we shoot everyone who is in their military and US citizens? What if we go to war with the Phillipines? What do we do with all the Filipinos in the US military? If they are captured, would we insist they be treated according to the Geneva Conventions?
It's good sport to make Walker our "two minutes hate." If you are going to do that, think it through a bit more. He should be prosecuted under the laws exixting at the time he enlisted in their army. If he is a POW, then he gets POW treatment, just as we insisted the NVA treat our aviators who were bombing their country without a declaration of war.
Walker KNEW he would be fighting against Americans, that was the stated goal in the terrorist training camps. Sorry, I'm not buying what you're trying to sell.