This is going to sound vague but I hope it’s somewhat helpful. Make peace with it. Acknowledge what happened, accept that he was rude, and learn from it. It feels like you are already on that road. You recognize now he was being rude, and you feel like you realize the school was too pretentious for you. Take it as a learning moment and look out for it in the future.
Yes we have a serious problem with that. I’m not sure what that has to do with a large threat like 9/11 though. We lost 3000 Americans in a day. We can discuss that without having to bring in every problem at once.