"Well, it is pretty hard to criticize a guy for dropping the "Nazi" bomb when..."
Confusing, isn't it? I'll try to clear it up. Mentioning the nazis is referring to history. If millions of innocents weren't deliberatedly killed, not even a hundred thousand, then 99 times out of a hundred, the comparison doesn't fly. If millions were deliberately killed, the comparison is very appropriate. In that light, it's not that complicated.
Or are you going to tell us there have been millions deliberately killed?