What were the reasons the bomb should not have been used on japan? should the atomic bomb have been used on japan? why or why not?

The reasons for it not to be used can definitely be the collateral damage where around 150,000 civilians died. On the other hand, the atomic bombs can be said to have ended to war in Japan since it capitulated, allowing everyone to focus on Germany. It also prevented much greater losses since a military study of a Japan invasion pointed out that millions of people would die. Compared to that, 150,000 doesn't seem that much.