Or if they dressed up as native Americans and sneaked on board a British ship and dumped all the tea in the bay?

According to some:

There are multiple, conflicting explanations for Atta's behavior and motivation. Political psychologist Jerrold Post has suggested that Atta and his fellow hijackers were just following orders from Al Qaeda leadership, "and whatever their destructive, charismatic leader, Osama bin Laden said was the right thing to do for the sake of the cause was what they would do." In turn, political scientist Robert Pape has claimed that Atta was motivated by his commitment to the political cause, that he was psychologically normal, and that he was “not readily characterized as depressed, not unable to enjoy life, not detached from friends and society.” By contrast, criminal justice professor Adam Lankford has found evidence that Atta was clinically suicidal, and that his struggles with social isolation, depression, guilt, shame, hopelessness, and rage were extraordinarily similar to the struggles of those who commit conventional suicide and murder-suicide. By this view, Atta’s political and religious beliefs affected the method of his suicide and his choice of target, but they were not the underlying causes of his behavior.

Keep in mind none of the above actually examined the man face to face in so far as I know.

I am sure he felt perfectly justified in his own mind for his actions and did not in the slightest way paint himself as the bad guy any more than Hitler or Stalin painted themselves in such light...or for that matter George Washington or Boudicca or Spartacus or any other number of people who resort to violence to solve their problems etc etc.