Get real.
If you'll notice, Donald's post was related to "quagmire," and political failure in Iraq, far more than just casualties, and this was my primary reference to leftist delight. Donald would cheerfully see Iraq go back to tyranny and chaos if it meant Bush going into the crapper in November, and he's not the only one by any stretch of the imagination.
But when it comes to casualties specifically, I suggest you go back over Donald's posts for the last few months. He doesn't exactly drag himself regretfully to the keyboard when casualty figures come in.