They still would have to fear, that someone leaks the video of it - and some superior needs a scapegoat to punish, because everyone here respects human rights etc.
A legally owned slave, was legally OK to be raped or killed. And ok to proudly tell everyone about it.
Is it really a deterrent, though? You said yourself that it'd be scapegoated and its not like they depend on good PR to keep their goodies, they own the country after all.
Also I can't help but wonder what these people talk about behind closed doors, do they really play by the same rules you and I would be held accountable to behind closed doors?
They still need good relationships with the west. Open slavery would not be tolerated.
Humans are amazing at justifying actions. There's a whole school of ethical thought devoted to it (utilitarianism).