So we have no reason to withdraw, and we will not do it. We will not sacrifice the interests of ourselves and our friends and our allies for the sake of people in other countries who don't happen to like it, and even if we were so inclined, we would not do it at gunpoint, because that just rewards their behavior.
As to attacking another nation, I don't see how you can say it is not justified merely because they are not attacking us. If that were the case, then any nation could simply protect and support private citizens in their borders to attack other nations, and no nation would be justified in using military force to fight back. I can't see how that logically follows.
And yes, more people will certainly take their place. This is not a reason to not act, but a challenge for the future to be overcome. I don't pretend that we can kill them all, that we can stop them from trying again, that we can stop them if they do try again, that military force will be solely effective. Military force is the least important act of what needs to be done, but it is, in my estimation, necessary. What will be more important are having our allies and our friends and the other members of this "coalition" doing what they can in their own countries to fight the battle. That is the key. Without it, we're kinda screwed.
And the reason the "Western press" has not said how many have died is because there is no way for them to know! Not even our military knows, probably.
A nation is not an artificial construct. I won't explain it to you, though, because I figure you would know what I say but merely disagree. And unfortunately, you can't buy me a beer, because I don't drink -- one more thing we disagree on! -- but the events of the last month have more than once tempted me to start. But I will gladly accept a root beer, either before or after my team beats yours in the next Quiz Show.