Are nuclear weapons that special? I am not saying 'are nuclear weapons really that bad', I fully believe they are horrifying. But I am asking 'are nuclear bombings that much worse than other mass bombings'. Consider the firebombing campaigns, Dresden, etc. Those were also indescribably horrible to live through.
I see an argument that nuclear bombs are 'too easy to use', making their existence horrible. But I don't see why the bombings of Hiroshima and Nagasaki get a special place (other than symbolic) when compared to other mass bombings of population centers. All such bombings are horrifying and evil.