It hasn't been disproven. There are video clips of it that was shown on 9/11 and surpressed shortly afterwards. It's easy to find on youtube now. But I assume you're not saying such video doesn't exist. By "disproven" you probably mean it's been "proven" that the video shows something else. The first version of this I heard around 2003 and said the Palestinian celebration video was just showing a wedding celebration. That's ridiculous, of course, to anyone who sees the video. There's another version now that says cameramen offered Palestinians candy to randomly celebrate for the camera. That's not such an outlandish claim since there's plenty of evidence that Palestinians are accostomed to playing for cameras (Pallywood). However, even in this version, the Palestinians are celebrating 9/11, right?

I understand that it's important for Palestinian supporters to paint them as sympathetic and that acknowledging Palestinians celebrate terrorism and the deaths of thousands of innocent people harms that cause. Consequently, Palestinian supporters sometimes make attempts to deny the obvious: Palestinians support terrorism.

Palestinians name their schools after suicide bombers. Why is it difficult to believe the people who name their schools after suicide bombers would celebrate 9/11?

Let's be honest:

The Palestinians celebrated 9/11. They celebrated 9/11 because they were happy about it. They were happy about it because they see the U.S. as the "great Satan" supporting Israel the "little Satan." They celebrate successful terrorist attacks against either the U.S. or Israel. Every sentence I've written in this paragraph is well-known and obvious, even to everyone on this thread.

It may be useful propaganda for Palestinian supporters to pretend the Palestinians didn't celebrate 9/11, but it doesn't change the obvious truth.

@tins: I took very little interest in the Arab-Israeli conflict before 9/11. Seeing the Palestinians celebrate on 9/11 was a turning point for me well. That's when I started reading about the conflict and realizing what a cartoonish version of the conflict is typically told.

Maybe those of you who support the Palestinians should learn something from those of us who side against them in the post-9/11 world. Maybe it's worth your while not to create more people like me. One way to accomplish this might be to try to train Palestinians not to celebrate and reward terrorism. Otherwise the next time there is a major terrorist attack and they celebrate it, there will be more people who see it and think: who are these monsters?