It was more than that. The spanking was symbolic of the fact that Caddy no longer viewed Semi as some form of monster, to be in awe of. This is the only way Semi has been seen by others for....well, thousands of years really. Hell, us wotmaniacs have for years positioned Semi as the singularly greatest example of sadistic-evil that exists in the series. We've been in complete awe of her, and we are looking in from the outside. The WoT people don't have the insight we have.

From her history during the AoL, straight through to the present, she alone has been the "monster", the sadist...she's pretty much the real-world equivalent of Satan.

Imagine Satan turning up tomorrow, to only have the world laugh at him and scold him like a child.....he'd be pretty put-off by that I would think.

Semi endured the previous punishments due to her knowledge that those punishing her were afraid of her, and therefore inferior to her. This fueled her ability to remain stoic and "take-it" as it were.

Hardly...you've simplified the nature of Semi, the nature of Caddy, the history involved...into a spanking. I think if you can get yourself to look past the spanking as the "holy grail" of breaking Semi, and realize that the spanking was symbolic of what was the true reason, your hatred (that's pretty strong word btw) for this scene would lessen. The reality is that Semi is just a human, with human flaws and emotions. Her wall of sadist/torturer/monster was what gave her strength....tear this wall down, and she's no different than anybody else.

The final comment I'll make is that in reality it was Sorilea who figured this out, and clued Caddy in. Sorilea ignited the idea of treating Semi as nothing more than another human, flawed like everyone else. Caddy gets the accolades, but it should be Sorilea getting the reward.