Enduring pain is one thing, but Lady Edyn prefers that her slaves go that extra step and tell her that they like it. It's much more pleasing to her to watch her slave suffer as she shocks his cock and then hear from him how he enjoys suffering for her. It's a true sign of subservience and obedience after all when a man suffers and claims to enjoy it. Whether he actually does enjoy it though is largely irrelevant, he just needs to please Lady Edyn by saying that he does.