Nothin wrong with a discussion like this aslong as no-one enters it to start flame wars etc. As soon as it starts getting out of hand the thread will be deleted. As far as any blanket bans on any discussions .. im not into that. Each case ,whereby a topic gets out of hand, is treated individually. Nothing is out of bounds, aslong as its legal 
It is important to understand the causes of September 11th . The terrorists arent just raving lunatics. Evil yes...but what has caused this hatred towards the UK/US etc is important to understand if we are to correct the problems. It doesnt matter what Osama Bin Laden's personal objective is , whether it be to free the Middle East or to turn the world Islamic , if what we do around the world breeds people willing to commit suicide for him. I recommend looking up Michael Scheuer the ex head of the CIA's Bin Laden unit and checkin out his views/books and of course Ron Paul , republican presidential candidate , heck even the 911 Commission Report. You wont learn anythin from Fox news etc.
Finally i wish all the best to the millions of victims resulting from 911.
EDIT : recent video of Michael Scheuer on ,ironically(after what i said above), Fox news
http://www.youtube.com/watch?v=qZNfuIvtLos
"Government is the great fiction, through which everybody endeavours to live at the expense of everybody else."
Frédéric Bastiat