I agree.
The movie doesn’t handle all this as well as it might have, but Leslie Groves’/Matt Damon’s remark towards the end is important. He is asked by the review board deciding on Oppenheimer’s clearance whether, in retrospect, he thinks Oppenheimer should have gotten a security clearance in the first place. He answers that — in retrospect — he wouldn’t have cleared “any of them,” meaning that the whole project was so riddled with security risks that in anything other than an extreme wartime crisis situation, a LOT of people shouldn’t have been cleared.
Too much of this is left in the shadows in the movie, and in the histories of the period, which tend to focus too narrowly on the Oppenheimer case (and sometimes Klaus Fuchs and David Greenglass). It would be interesting to know, for example, how many people were considered for the Manhattan Project and refused a clearance. That would put Oppenheimer’s case in better context.
My open question has for years been David Greenglass. How the heck did he get assigned to Los Alamos, given that Julius Rosenberg was already running a significant Soviet industrial espionage ring, and given that Greenglass’ personal history was also highly problematic? I’ve always wondered if Greenglass was placed, and if so, by whom. Klaus Fuchs at least had scientific expertise that could plausibly have led investigators to give him the benefit of the doubt. But Greenglass was a machinist — a highly skilled one, I’m sure, but still ... — and his background, along with his sister and BIL’s, should have triggered a closer look. Were security really that sloppy, or was Greenglass placed?
As for Manhattan Project security, the need for physics and math talent was so great that a lot of people were recruited and waved in in spite of security issues. The intense security that surrounded the project was thought to be a way to hedge against the ensuing risks.
There is reason to suspect that FDR's aide Harry Hopkins was a Soviet spy and sent A-bomb secrets and materials directly to the Soviets. Washington had numerous Soviet spy rings, with many of them escaping detection and prosecution. Most historians seem disinclined to pursue such troubling issues for fear of what might be found.