I don't think it is really possible to understand the 9/11 sentiment if you weren't cognizant during it. Boomers, GenX'ers, Millennials all seem to recognize how shocking it was but in a post-9/11 world it exists only as history and it doesn't compare to something like Hiroshima and Nagasaki or Dresden or even the Blitz. And of course not the Golden Cow which we are forced to read about every year in school.