Eek...
What's with the "kill'em all!" attitudes... they pop up every now and then, mostly as a joke, but sometimes as a serious suggestion.
Here's why: We supposedly kill terrorists, because they're doing wrong (by killing civilians) and we're doing right by killing them.
We are killing them all the way over in Afghanistan, because they are still a threat locally (they aren't any more a threat to the US, than any eager anti-american, anywhere in the world. North Korea is a bigger threat than the Taleban)
So, by implementing a "kill'em all" attitude, you have basically reduced a war with a cause, to being a war solely for the fun of killing. Basically, a real life FPS or something, only with 90% civilian encounters. In other words, you are now the terrorist.
I don't know how this is something that needs to be explained to people, but apparently it does.