They didn't know of the effects the bomb would have on the hibakusha. As far as I can tell, it's the severe discrimination they received at the hands of their

They didn't know of the effects the bomb would have on the hibakusha. As far as I can tell, it's the severe discrimination they received at the hands of their countrymen that was/is their biggest problem, e.g. as Wikipedia puts it, "The government of Japan recognizes about 1% of these as having illnesses caused by radiation." The physical injuries we inflicted with the atomic bombings were on a par with our systematic firebombings of their cities, especially when everything came together and a firestorm developed, like in the first firebombing of Tokyo that killed 100,000, and Hiroshima.