It's still an oversimplification.
One can have a clear Deontological sense of right and wrong, and then decisively and without hesitation choose to commit an evil act (eg. murder Hitler) for the greater good. IMHO, the difference between the Deontologist and the Utilitarianist (or Consequentialist) is that the former accepts responsibility for his actions rather than try to excuse them.
(why has my inner voice started singing "Immanuel Kant was a real pissant..."?)