Final answer:
Mullah Omar argued that Afghanistan is not responsible for the September 11 attacks because the attacks were planned by Osama bin Laden, but carried out by individuals and not the Afghan government or people.
Step-by-step explanation:
Mullah Omar argued that Afghanistan is not responsible for the September 11 attacks on the United States because although the attacks were planned by Osama bin Laden, who was living in Afghanistan at the time, they were not carried out by the Afghan government or the Afghan people.
The Taliban government, which was in power in Afghanistan, did not have direct involvement in the attacks. Additionally, there were no credible evidence or connections proving that the Afghan government or people played a role in the planning and execution of the attacks.