I think the only good reason was to bring the war to an end.
Nobody was against it at the time....the Japanese were planning on fighting the allies till the last man...(in their entire country). A reason against it would be that God does not want us to kill our enemies. The Bible says to love your enemies, not kill them.
The advocates against the use of atomic bombs mostly referred on the civilian casualties, the illness it brought and the devastation.
If you are referring to WW2, then the US stopped using atomic bombs on Japan because Japan agreed to surrender. Had they not, the US had plans and production setup to drop a total of 23 atomic bombs on Japan in 1945.
Invading it the conventional way would have cost many American lives, and the US decided it was better to just kill of a load of Japanese people instead.
To save the lives of American GI's who were slated to invade Japan.
If the tested bomb had not worked it is likely they would have tried dropping the other bombs.If Japan had surrender prior to the dates the bombs were to be dropped then the bombs would not have been dropped on Japan.
Radioactive waste would cause unborn babies to die/ have mutations.
Albert Einstein had almost nothing to do with creating atomic bombs, and he opposed using it. The Manhattan Project had over 50,000 people employed in the task.
Nothing, you can't stop using something you haven't started using. The only country that has ever used atomic bombs is the US, that was to cause Japan to stop fighting during WW2; when they surrendered the US stopped using the atomic bombs on Japan.If instead you really meant "What prevents countries from using the atomic bomb?"; that is a far more complex question to answer.Most countries are prevented from using atomic bombs simply because they don't have them. It costs a significant investment to set up the infrastructure needed to make them and few countries wish to make such an expenditure when they have higher priorities.Formally, many countries are prevented from using atomic bombs because they have signed treaties against using them. But they could either choose to withdraw from or abrogate these treaties at any time, so such treaties only prevent a country from doing what it isn't planning on doing anyway.Some countries are prevented from using atomic bombs by public opinion.It has frequently been claimed that fear of nuclear retaliation prevents countries armed with atomic bombs from using them on each other. One form of this idea is called MAD. However one can never be certain that a leader with no such fear might come to power in a country and just attack anyway.etc.
August 1945
It would have been possible for the US to defeat Japan without using atomic bombs, however, there was a strategic reason for using the bombs, which was that Russia had entered the war and was intent on occupying Japan in much the way that they took over eastern Europe, and note that there is still one Japanese island occupied by Russia to this day, in 2011. So the US, which even before WW II was entirely over was already making plans for the Cold War to come, needed to bring the war with Japan to a rapid conclusion, and they were able to do that by using atomic bombs.