Hirohito personally ordered the use of Phosgene gas during the battle of Wuhan. He was far more involved than the imperial palace or MacArthur ever acknowledged. Herbert Bix and others, have detailed how Hirohito's, and other members of the Imperial family active involvement in the War was covered up.
Today, we have a strong and loyal ally in Asia
As we do with Germany
Unlike the Germans, the Japanese did not elect the military leadership which led their country to disaster.
The Germans didn't elect the Nazi's to power, they only won 33% of the November 1932 election. It was only after the Nazi's had suppressed a number of the other German parties that they managed to pass the "Enabling Act" which made Hitler a virtual dictator. The Japanese had general elections in 1932,36,37 and 1942, although like the Germans in 1933 by 1942 they effectively had a popular military dictatorship.
Finally, had your bloodthirsty "solution"..
At least my solution would have been endorsed by the USAAF pilots (and their families ) who when captured were the subject of vivisection by the japanese.
I'm glad Abe Lincoln and General Grant didn't have a similar vision.