You are correct in this. The Left (including the media) has been pushing the "inhumane/racist/unnecessary" line since the end of the war.
I read a book by the incomparable Richard Feynman (a wunderkind 27 year old physicist working on the Manhattan Project, one of the youngest who was in intellectual step with the likes of the old guard geniuses like Bohr) where he said that a lot of the moral handwringing during the project is overwrought and overstated as it is shown in stupid movies and books by Leftists since then. He has maintained that people were there doing a job, and nearly everyone was onboard, working to get the job done.
I believe the truth of calling the use of the weapons "inhumane, racist, and unnecessary" is as responsible for people who have disowned it or distanced themselves from it since 1945, is much the same dynamic as people who say things today who take stances on racism to avoid being labeled as racists.
Many of them didn't want to be held responsible for creating the weapon if we got into a nuclear exchange where hundreds of millions of people would die. (this is my opinion on this, not a stated fact)
Indeed. All of the scientists were on board. I know this because my family was there. One of them was a 21 year old who was given sole responsibility for the design and computations for one component of the bomb. He would later work with Teller and Samuel Cohen on the hydrogen and neutron bombs respectively. In ‘48 it was he who informed Truman that the Soviets were weeks away from testing their bomb and stationing an observatory In Alaska was needed. Under Reagan he led the study advising going forward with the Strategic Defense Initiative (Star Wars) which forced the Soviets to compete financially eventually leading to bankrupting them. Revisionists are evil in the most Biblical sense.