Agreed - it was just a slighly jarring - and as always slightly embarrassing - moment to be confronted with bonking and tits for no good reason, in the midst of a serious film. I honestly don't know why directors feel they have to do it. I'm sure that most in the audience don't really like it much and it can't be fun for the actors and especially perhaps the actresses.
But overall it was thought-provoking which I suppose is the sign of a good film. I've been looking up Blackett. Seems he got the Nobel Prize for some very clever experimental physics involving cloud chambers to track subatomic particles. So he was an experimentalist rather than a theoretician, whereas Oppenheimer wanted to learnt the theory of the new quantum mechanics. Blackett seems to have been very demanding as a supervisor, too, so it's not surprising they didn't get on. Blackett's politics were very left wing, though he seems to have been a socialist and not a communist. In the circumstances, though, I doubt he would have influenced Oppenheimer's politics.
Another interesting point in the film was that quantum mechanics was an entirely European achievement. I'd never really thought about that, but indeed the big names: Planck, Bohr, Einstein, Schrödinger, Heisenberg, Dirac, de Broglie, Born, Wigner, Pauli.......are all European and mostly German-speaking. (They gave Bohr the wrong accent in the film, though: he was a Dane). Oppenheimer was thus the evangelist who brought QM to the US.
In a way, the film is the story of the US catching up and then overtaking Europe in physics - largely thanks to one A Hitler!