The former President of the US, Eisenhower, said that the nuking of Japan was not necessary.
As other posters have pointed out, Ike was not in the decision-making loop. It was confined to Truman, his Sect. of State & several other close advisors. Read David McCollough's excellent book on Truman for details on this.
I think you misconstrue Ike's later comments about the bomb. He regretted that it was necessary & speculated that the war might have been won without it, but did not say that he would have recommended against it at the time (had he been in the loop.)
In any case, recently declassified info, including that cited in the article, show that Ike was wrong.
At a minimum, the bomb saved the lives of 100,000 American POWs who were held in Japan at the time of surrender.