I disagree with this. This is not a war, not an occupation; It's more of nation building. The amount of casualties - while tragic - is limited;
More US Marines die in the US on the back of crotch rockets than die in Iraq.
Sixty years after WWII we are still in Germany and still in Japan. It has nothing to do with Iraq or even Afghanistan, but instead sends a message to the rest of the world - if we come knocking on your door, we'll be there sixty years later. We need to send a message that says "We won't leave".
Just my two cents.