So you are okay with killing, but you have a problem with waterboarding, which causes no harm?
First of all let me repeat: Water torture
does cause harm. If you think otherwise I suggest you try it.
Second: Yes Nuke, if you have to kill someone do it, but do it as humanly as is practically possible. Don't make people suffer if you can avoid it, even the enemy, and even if the enemy is not so generous. If you capture a terrorist on the field of battle that you are within your rights to execute him for his crimes, but not to torture him. I know you don't get this, and that's sad.