Long ago, in another life, I played the Reverend Hale in 'The Crucible' and from that I have a real sense of what motivates neo-cons and the like - Miller is good on the virtuous, but he is also brilliant on the righteous and their terrible sins and occasional bitter repentance. I loved the man and his plays, and his capacity to go on when almost everything he cared about broke in his hands. Except, though I am not so much a fan of the later plays, his talent.
The important thing is not that he loved Marilyn; it is that, for a while, she had the sense to love him. God, they both had good taste.