re: Why is Betty Draper (Mad Men) such a cnut?

The episode - Chrysanthemum and the Sword hints at possible molestation of Sally by the grandfather and the requisite guilt by Betty for allowing her father to live with them - it tends to be leading to that when Sally cuts her hair and is caught masturbating and Betty flips out and wants to cut her fingers off and they both go see the psychiatrist. The inference is that Betty herself knows what her Dad is capable of and has repressed it - flashback to an earlier episode when the Dad grabbed Betty's chest in a sexual manner (albeit confused.) Sally was later angry at the Grandfather passing and was way to sexually aware at age 10.

It's all conjecture and it never panned out - but a lot of people thought that is where they were heading in that direction to explain some of Betty's problems.

But I also think that's part of the genius of Mad Men - like life, they don't spell it out but leave it up in the air - untidy but there.