US army to Osama: What do you want to say in your defence? 
Osama: I am not guilty for 9/11, pilot was inexperienced.
Who are you trying to blame on 9/11? This joke isn't okay.
To me that is funny like shit. People just automatically assume if you ask a question like this, you must support the terrorists. I don't think I have to explain anything more.
It's still quite disrespectful and a fresh wound to countless of victims. It's not a good idea to talk about 9/11 in such a way, so it would be better to cherish and memorialize the victims and respect them.