Does Kesey really argue that women are less powerful than men? Why is it that Nurse Ratched loses her power when McMurphy reveals her breasts?

I think there is scene is more complex than women being shown as weaker. Nurse Ratched is merely made to look human. Her androgynous front is ripped of to expose who she is. McMurphy’s attack on Nurse Ratched is about power and sexuality. He effects a literal and figurative exposing of the Big Nurse. When he attacks her, he exposes her breasts, the one barely suppressed sign of her femininity. This point also relates back to Harding’s earlier suggestion that sex is the cure for Nurse Ratched—here it is at least a cure for the men against her. The result of this fight is the final humanization of Nurse Ratched in that everyone learns what McMurphy has known from the beginning: she is human and weak and troubled like everyone else. When she returns to the ward after the fight, she is unable to speak and thus has lost a major sign of her power.