He was a commie sympathizer.
Because commie chicks are easy.
He was a brilliant man for sure.
However he was also an example of one of those scientists who was totally gung ho to develop a weapon to use against the Germans, but suddenly developed a conscience when it became clear that it would also threaten the motherland.
I would love to have been a fly on the wall when Truman said “get this SOB out of my office!”
He was a commie sympathizer.Which he freely admitted.
OTOH, many of the rocket scientists behind the strategic missile program were former Nazis.
Based on what I've read, the movie is more an indictment of the AEC chairman who just happened to be a Republican.*
Whatta shock. 
Even worse, there is reason to suspect that Oppenheimer was a knowing spy source for the Soviets. Vasili Mitrokhin, a former KGB archivist who defected to the United Kingdom after the fall of the Soviet Union, saw documents that indicated Oppenheimer provided key technical details of A bomb design and construction to a Soviet spy.