Maybe, but your argument was "absolutely not necessity" which I think is untrue. Now if your argument should be interpreted as "violence is never necessary", Tolstoy-like pacifism, rather than "necessary" in any utilitarian sense of the word, then I respect your (I would argue) correct interpretation of the Gospel, and I see where you're coming from. I just think many people will misunderstand your original note without that context.
Discussion
Mind you, the original tweet wasn't mine.
But it wasn't necessary in the sense that the Japanese had already surrendered.
Speculative "what if"s aren't relevant in this
How would you convince someone that the Japanese had surrendered before the bombs?
Was pearl harbor necessary https://www.history.com/topics/world-war-ii/pearl-harbor
I think perhaps the Japanese had show willingness to a conditional surrender, but that the US would only accept unconditional. I believe that the US is the most uncompromising and dominant empire we've seen since Rome, and Hiroshima strikes me as a Carthage or sacking of Jerusalem like moment in establishing hiarchey as a global hegemon in a history defining way. In that sense it was necessary (from the point of view of a US imperialist) It was needed to break the spirit of the Japanese and subdue the entire region (even world) to US power. But in terms of being necessary in the strict sense of simply ending the war, you are probably correct in that it wasn't needed. Not sure if the "pax Americana" would have lasted without the psychological edge it gave the US for decades after, although the value of the so-called "pax Americana" is itself something that can be debated, I am aware.
Evil doesn't justify evil...
Dominating the world isn't an excuse