1937 Yet another incident reignites the war, leading to the capture of Shanghai (https://en.wikipedia.org/wiki/Battle_of_Shanghai), the capture of Beijing, and the capture of Nanjing (https://en.wikipedia.org/wiki/Nanjing_Massacre): ("Because of the myriad of factors, death toll estimates vary from 40,000 to over 300,000, with rape cases ranging from 20,000 to over 80,000 cases. However, the most sophisticated and credible scholars in Japan, which include a large number of authoritative academics, support the validity of the International Military Tribunal for the Far East and its findings, which estimate at least 200,000 casualties and at least 20,000 cases of rape.").
"Some historical estimates of the number of deaths which resulted from Japanese war crimes range from 3 to 14 million through massacre, human experimentation, starvation, and forced labor that was either directly perpetrated or condoned by the Japanese military and government." (https://en.wikipedia.org/wiki/Japanese_war_crimes)
Now, I realize you've said you acknowledge Japan's war crimes, and you might even invoke the sunk cost fallacy: those people were already dead. However, there are two points you seem to be missing: the goal of the allies with their "unconditional surrender" terms were the removal of governments that had repeatedly demonstrated that they were militarily aggressive and their replacement with governments that were not (successfully, I might add), and by the scale of Japan's own actions in the war that "discomfort" is a drop in the bucket.
That decision had been made long before 1945. A pocket timeline of the Second Sino-Japanese War (1937 (officially) - 1945) (https://en.wikipedia.org/wiki/Second_Sino-Japanese_War)
1931 Japanese military manufacture a casus belli (https://en.wikipedia.org/wiki/Mukden_Incident) and invade Manchuria, defeating the Chinese and occupying it. (https://en.wikipedia.org/wiki/Japanese_invasion_of_Manchuria)
1937 Yet another incident reignites the war, leading to the capture of Shanghai (https://en.wikipedia.org/wiki/Battle_of_Shanghai), the capture of Beijing, and the capture of Nanjing (https://en.wikipedia.org/wiki/Nanjing_Massacre): ("Because of the myriad of factors, death toll estimates vary from 40,000 to over 300,000, with rape cases ranging from 20,000 to over 80,000 cases. However, the most sophisticated and credible scholars in Japan, which include a large number of authoritative academics, support the validity of the International Military Tribunal for the Far East and its findings, which estimate at least 200,000 casualties and at least 20,000 cases of rape.").
Some additional info: https://en.wikipedia.org/wiki/Contest_to_kill_100_people_usi... https://en.wikipedia.org/wiki/Nanjing_Massacre#Rape https://en.wikipedia.org/wiki/Nanjing_Massacre#Nanking_Safet...
(I mention those because they make it perfectly clear that the Japanese people knew about the activities of the military in China.)
These activities resulted in an international response (https://en.wikipedia.org/wiki/Battle_of_Shanghai#Internation...), but nothing resulted until after the Japanese takeover of what was then French Indochina. Then, trade restrictions and an embargo resulted in Japan's attack on the US (https://en.wikipedia.org/wiki/Events_leading_to_the_attack_o...).
"Some historical estimates of the number of deaths which resulted from Japanese war crimes range from 3 to 14 million through massacre, human experimentation, starvation, and forced labor that was either directly perpetrated or condoned by the Japanese military and government." (https://en.wikipedia.org/wiki/Japanese_war_crimes)
Now, I realize you've said you acknowledge Japan's war crimes, and you might even invoke the sunk cost fallacy: those people were already dead. However, there are two points you seem to be missing: the goal of the allies with their "unconditional surrender" terms were the removal of governments that had repeatedly demonstrated that they were militarily aggressive and their replacement with governments that were not (successfully, I might add), and by the scale of Japan's own actions in the war that "discomfort" is a drop in the bucket.