I agreed with you Methodis for the reason that it prevented Russia from splitting up Japan. That would have been pretty bad.
You also have to realize, if we didn't drop the bomb, we would have lost thousands of americans invading Japan.
If you were Truman at the time, would you pick.
Option A: Drop the bomb and end the war, while showing the Russians that America means business.
Option B: Invade Japan, costing thousands of americans and Japanese soldiers their lives? Who knows if it would have even been successful.