Le May had to resort to bombing 'areas' / cities in Japan I think in part because it proved impossible due to the effect of the jet stream that the B-29's flew in, to bomb accurately with the bombing computers then available.
Just finished reading
The Man Who Flew The Memphis Belle, by Col. Robert Morgan (Ret.) USAFR
The latter section of the book deals with Morgan's return to combat, flying B-29's in the PTO. The subject of Le May and the firebombing raids does come up, as do the difficulties of high level bombing in the jet stream over Japan.
A change of tactics to low-mid level bombing was required to improve accuracy, but the fire bombing was not begun as a counter to inaccurate bombing, but because a couple of hundred B-29's dropping incendiary bombs on cities built primarily from wood could completely and utterly raize anything from 5-25 square miles of a city, with damage spreading much further.
Japanese cities tended not to have industrial and residential districts either, with industrial targets often literally right next door to densely populated residential areas.
Combined with the projected casualties of an Allied invasion of the mainland (1 million+), and the knowledge that more or less the entire population would sacrifice themselves in the defence of the homelands, firebombing was seen as the most effective strategy for the bombing campaign over Japan.
As others have stated, applying 21st century morality to 1940's warfare is neither fair nor right. As I was born over 30 years after the end of WW2, I shall leave the "right or wrong" debate to those who were there.