What rot - the residents of Hiroshima would have cut off just as many Chinese heads as the Japanese soldiers did in Shanghai, without a single resistor.
Your understanding of the national Japanese character of WWII is beyond naive.
More so, the citizens of Hiroshima, and many another town, were indeed responsible for the atrocities their sons inflicted on Asia. Japanese were not quite like the Germans, who comparmentalized their mass murder and left the army to fight (with a degree of “honor”) and the SS/Gestapo to do nearly all the dirty work.
The Japanese military, the privates and NCO’s, did most of the nasty stuff directly and personally.