I also think, the human tendency to take the path of least resistance often leads down the path of fear and ignorance as you stated. It is simply easier to assign a sweeping generalisation and make simple, linear conclusions based on said assignment. After 911, I admit, I hated everything about the Middle East and parts of Asia. It was simply easier to hate and wish doom to entire nations.
After my experiences, I have come away with a much different conclusion, and it is a hard pill to swallow. I am more uncertain of humanity than I ever have been throughout my entire life. I simply do not know or have no answers. This is in stark contrast to believing I know (albeit falsely) the way of the world and the rational for human motivation. However, I would rather be uncertain in my assessments and musings than absolute and incorrect. Like you, I have had difficulty in explaining my change of heart so to speak. I can only say that if fathers in Afghanistan love their daughters and weep over their daughter's broken bodies, then perhaps the simplistic view that every person from Afghanistan is a terrorist waiting to kill Americans is grossly incorrect at best.