Usually we think of spanking as a punishment, but many slaves get excited and hard when spanked... so is it really a punishment for the slave?
I'm part of the spanking community in the States.
1. Spanking is used as a punishment sometimes, yes. But it is also used as play, as stress relief, and for numerous other reasons.
2. The only slaves that get hard when spanked are those with penises. The ones with vaginas do not.
3. Not only slaves get spanked. Subs and switches do. And I've known some Dom/mes and M types as well. A spanking is a physical act, and sub/slave/Dom, etc., are relationship concepts.
4. I agree with you that a punishment that makes the punished party happy doesn't work. However, I have heard of speakers that get aroused even if they hate the spanking.
The small-breasted ones want larger breasts. The large-breasted ones want smaller ones. The straight-haired ones curl their hair, and the curly-haired ones straighten theirs...
Quit fretting. We men love you."