I always got the feeling that Fred, before all this, was in Serenas shadow. That she helped him and 'the cause'. That she knew her place in the new world but did the right thing (in her eyes) and surrendered her power because she's a woman, to the man, Fred.
This is how I see it. Fred isn't used to the power and authority. It surprises him from time to time. He doesn't act in a way that he's used to it. He tows the line and does things by the book but it's not in his nature to be that person. When he beat serena, he told himself it was because that's what he should do, to hold his place and not what he wanted to do to hold his place.
Don't get me wrong, I don't like him one bit. But he raped June because serena told him to. He let serena scream in his face. Pre Galihad, she wore the trousers and he's used to that. He's not quite the right person to lead that relationship. He's only doing it because he's the man and that's what he should do.
I think Fred is weak. Pitch him against serena he is weaker than her.
Her vulnerability is wanting a baby. That's driving her. She said herself, she let him and supported him in his quest and all she wanted in return was a baby. She's so driven by that force that she can't see past it.
I think I even remember her being shot in a flashback, in a scene where she was a speaker at a university, supporting the new world and she got shot by a protester and so she lost her chance of having a baby because of her supporting Fred. What she wanted in return is what he ultimately took from her. He knows that. He feels he owes her that and will do anything to provide her that - even rape June, who I think he actually respects.
He doesn't realise how much June hates her because he is not emotionally intelligent. Because she doesn't scream, shout and protest he assumes she accepts him. He doesn't know she hates him because she is too subtle for him to pick it up.
He's naive with his relationship with Nick. With all his relationships. He forgets how his power controls people's behaviours around him and after so long, he doesn't realise the hatred people have for him because of his lack of emotional intelligence to pick that up.
I dunno. That's how I see it.