Theodore Hall was a traitor. He was a U. S. soldier who gave atomic weapons secrets to the USSR. But it's important to separate the film from the people it portrays.
The film is a documentary and hence is supposed to be educational. It accomplishes that. If you liked Oppenheimer and want to know more about the creation of the atomic bomb, and your interest in spies, communists and communist sympathisers who worked on The Manhattan Project was piqued. Hall was one of them.
Even though he knew of the crimes of Stalin, and the evils of communism in real life, he held to the ideological principles of Karl Marx. He gave the secrets of the atomic bomb to the Soviets because he felt an affinity for them. He wasn't the only one. Klaus Fuchs did too.
So if you thought the security precautions taken at Los Alamos were excessive, this movie will give you an appreciation for why they were necessary.