Well, first a disclaimer - Sheryl Crow vs Ann Coulter is like throwing retarded kittens to an alligator. You know how it's going to end and it ain't gonna be pretty.
That said, I'm with Ann on this one - not all of them, but this one to be sure. People who arrogate to themselves the right to kill 3000 innocent people to make a point have already dictated the terms of the relationship. It is neither irrational nor "unfair" to happen to be better at killing them than they are at killing us. While desperate cries of moral equivalency and invocations of past sins serve to muddy the water they really don't address the main point - if they're dead they can't do it again.
One wonders sometimes at the weird moral asymmetry that results in the notion that them killing us is justified where our killing them back is not. The rules regarding justification turn out to be incredibly plastic, but not the rule of a 500-lb bomb impacting the goat dip at a terrorist soiree. It's a little difficult to re-frame that one. The inherent inflexibility of that is no doubt anathema to the enlightened liberal mind but it works wonders for making Abdul aware that two can play at his game but that only one can win. What is most difficult to understand is why this seems to be so difficult to understand.