Not everyone wrote in support of the Committee’s aims. Criticisms of both their cause and their methods were abundant. Many felt that the scientists themselves were to blame for creating the danger of the atom bomb in the first place. A number of correspondents commented on the “peculiar irony” of the situation: as Morris Kellerman pointed out, it was “an ironic reflection upon our civilization that the scientists must now work hard to reconquer their brainchild.” For some, such as Emily Cooper Johnson, this irony led to significant hesitation about donating to the cause. It was difficult to send money to the same group of people who, as she wrote, “have devoted their entire abilities to creating the most destructive machine of all time, and who now...want aid in overcoming its dangers.”

Many donors thought that the same minds that created the atom bomb now had the responsibility to control it, but criticized the scientists for their specific statements. Chemist Joseph Kennedy protested the “facts” presented in the Committee’s main statement. Most of them, he writes, “should be classed as partly doubtful and partly wrong,” and he took issue with being included by the claim that “all scientists” supported these facts. Veteran Lewis Isaacs objected to the Committee’s "use of the term 'ethical' in connection with warfare," and that their claims seemed to "make moral distinctions between ways of killing and maiming.”