I understand why they were mad at America, too, and I accept the validity of that. However, I do not believe the bombing of the WTC was a valid output for their anger. Do you? And celebrating that sort of attack is quite a bit more different than celebrating the capture of the guy who planned it. IMO. Bringing up carpet bombing of Europe or whatever is a neat logical distraction, but we're not talking about the relative merits of WWII Allied tactics (which may or may not have been "just as bad" or whatever). We're talking about this specific instance.
I remember after 9/11, I wanted to kill him myself. And while I accept that his death has not made us any safer, and even though it took 10 years, I'm still glad it eventually happened and I think that every guy on the team that got him deserves free drinks from each of us for the rest of their lives.
It's cute to make philosophical arguments about the relative moralistic equivalences of two opponents in a war. But just because they have similarities doesn't mean they are both "equally right" or whatever. This is the same logical trap agnostics fall into.