The Dresden firebombing: "The precise number of dead is difficult to ascertain and is not known. Estimates vary from 25,000 to more than 135,000 dead. Such estimates are made very difficult by the fact that the city was crowded at that time by many unregistered refugees and wounded soldiers. The foreign forced labourers may represent a large number of dead, since they were usually employed in the squads to fight fire storms. (In comparison, some 100,000 died in the bombing of Hiroshima, about 50,000 in the bombing of Nagasaki and 100,000 in the bombing of Tokyo and 200,000 were killed in Warsaw during the Warsaw uprising 1944.)"

Source: http://en.wikipedia.org/wiki/Bombing_of_Dresden_in_World_War_II#Impact_of_the_attack

It is conceivable that Dresden was deadlier and/or more destructive than Hiroshima and/or Nagasaki. Frankly I don't care which act of war was deadlier - my point was there have been many horrible acts of war in the past, and we're not going to apologize for all of them, so why apologize for Hiroshima in particular?