They killed innocent people.
Not only was the warning to Japan only 5 days before the bombs were dropped, there were still innocent people in Japan. USA killed over 140,000 innocent people in Japan along with 2,000,000 people killed by radiation, not even considering the people who now are deformed and linked to cancer. That's way more than the bombs at the twin towers that killed around 3,000 people. No matter if Japan was supporting Germany, there were still INNOCENT PEOPLE that were killed. And I still know that Japan attacked Pearl Harbor, which had no innocent people (because they were all troops). Those people are DEAD for no reason.