Of course Comedians have made jokes about events such as 9/11, however they were hardly doing it when it happened. Secondly, Comedians make a living from telling jokes and some of them use use such things to deliberately be controversial, Frankie Boyle springs to mind.
The Dictator is a film that was released 11 years after 9/11 even took place and again is something that was hardly devoid of controversy.
Saying "LOL, stupid dead Americans" is just a pure insult, thats not even a joke. People making jokes about the situation, especially so soon are just after attention and think they are clever.
I'm wasting my time trying to demonstrate this to somebody who has made such a joke in this very thread, and doesn't even have the basic school Biology education to know that Humans have arteries in their legs.