When it comes to his moral compass, Sai Mun Chui Sheut is a difficult character to figure out. Is he a moral/ethical man? Some of his behavior suggests so. He believes in fighting honorably: he is unwilling to stab an opponent in the back (he was outraged at Seung Gwoon Dan Fung for stabbing Yim Teet San in the back), unwilling to attack an injured or weakened opponent, unwilling to attack an unarmed opponent, and limits his killing to those who deserve it due to their misdeeds (this last is questionable, however, as people such as Hung Tao, Soo Siu Ying, and Dook Goo 1 Hok, who died by Sai Mun's sword, didn't seem to be such bad people).
On the other hand, does Sai Mun Chui Sheut strike you as someone who would intervene to save an innocent person if doing so didn't interest him? For example, let's say SMCS encounters some bully (not a swordsman) beating on some elderly folks and little children with a wooden stick. If Luk Siu Fung or Fa Mun Lau (or any other hero in wulin) encountered such a situation, he would most likely intervene and protect the elders and children from the bully. SMCS, on the other hand, would see that the bully isn't a swordsman and has very crude fighting skills and...what? I'm not sure. Would he have no interest and simply walk away because swords and elite martial arts aren't involved, or would he do what a hero should and intervene to save those people from the bully? I'm really not sure.