J. Samuel Walker’s main argument against the use of atomic bombs is that

Atomic bombs were more destructive than conventional bombs
Am american invasion would not have been as destructive as the bombs
The war would have ended anyway
The japanese emperor opposed the use of atomic bombs.

The main argument against the use of atomic bombs by J. Samuel Walker is that the war would have ended anyway, and that the American invasion would not have been as destructive as the bombs. Walker argues that the use of atomic bombs was not necessary to bring about the end of World War II.