Arguments that the truth is ours and the lies are theirs are all basically worth dismissing offhand.
Except that in this particular case, that's exactly what's going on. We know Bin Laden was responsible for 9/11. We know he was responsible for the attack on the Cole and the African embassy bombings. We know he was responsible for any number of other terrorist acts. These are basic, irrefutable truths. The fact that none of those ordinary civilians in the World Trade Center were responsible, either directly or indirectly, for what has been going on in the Middle East for centuries is also a basic truth.
No it's not. First off, centuries? If you want to talk about basic truth you might want to pick up on your historical truths.

So if the citizens of certain countries want to spin it that they were, they're being self-delusional. As NGTM-1R noted, they're culpable just by being willfully ignorant. We don't even need to get into discussions about external vs. internal justifications...we're dealing with factual events, and the arrow points squarely in one direction.
You think that the people who celebrated 9/11 in Palestine and the rednecks who celebrate when Arabs get massacred are willfully ignorant? You think people get their opinions by rationally weighing all the available information and reaching a conclusion? Hell, do you think
you can do that? (You can't; nobody can.)
Constructing a world in which people who examine the same information you have and then proceed to disagree with you are morally wrong is going to take you some ugly places.
You're surrounded by Americans who believe the government ordered 9/11 and that the moon landing was fake, and they came up with those ideas in the context of our relatively transparent society. Imagine what it's like living under Hamas.
The assumptions said Palestinians grow up with, the things they learn from their environment, are fundamentally different from what we receive. Not only did they believe that 9/11 was justice done, they had every bit as much reason to believe it as we did to celebrate the death of bin Laden (and believe me, I was glad when bin Laden died) - namely, the reason provided by the combination of available information and the worldview created by their environment.
Hell, I can see where they're coming from. We live in a democratic government; our citizens are surely responsible for the actions of our leaders, right? And no, that's not the same as agreeing with them - counterargument is pointless unless you can argue why a Palestinian wouldn't believe this.
I don't think they were right, but
they think they were right. The argument here isn't even that we have equal claim to be right - it's that our respective celebrations of these respective events proceeded from very similar beliefs.
I don't really give a **** about what a bunch of ass-backwards types halfway around the world happen to believe is justified. Bin Laden was a mass murderer. He's dead now. You can bet your ass I'm going to be happy, and you can bet your ass I see no moral issue with being happy.
Ignoring what a bunch of ass-backwards types halfway around the world happen to believe is justified is exactly what got us into this mess in the first place.
Killing a man is never worthy of celebration. Sometimes, however, it is necessary; and that necessity should be met, perhaps, with satisfaction at a job well done, or relief at the (possible) prevention of future disaster, or knowledge that the punishment of a crime will, if all goes well, deter future crime. Celebration, though? That's a lot. In fact, that's glorifying bin Laden - making him into more than he was. He was a criminal, and in the end he died a criminal's death.
The biggest blow we can deliver to terrorism is to render it insignificant and go on with our lives. bin Laden rose to prominence because of his reputation for courage on the battlefield fighting an invading enemy. He wanted to be a leader of men and an implacable foe to occupiers. Celebrating his death at the hands of a foreign army is exactly what he'd want; nodding and moving on is exactly what he'd fear. Terrorism feeds on a cycle of violence and outrage, after all.
So, as for my own reaction? I was satisfied. It was a kind of closure. Do I think dancing in the streets in celebration of bin Laden's death was morally equivalent to dancing in the streets in celebration of 9/11? Not really; I see a big difference between celebrating the punishment of a criminal and celebrating a blow to a foreign occupier which involved enormous amounts of collateral damage (and no, that's not MY view of 9/11, but it's probably what those street dancers thought). But I feel that no matter how much better reason we might have to dance and celebrate, there's too much in common for me to be comfortable with it.