It's awful, isn't it? Her entire story is about treating her like a person instead of an animal, up until you suddenly have to treat her like a performing animal for the jollies of a scumbag.
At the risk of butting into something I may have misread, if this is about Cornwall's sex-a-thon (hey, I pay attention to more.. important parts of the game than things like stat levels >.>), I think this is blowing things out of proportion.
It's not content that I enjoyed, period. But the dialogues preceeding as well as during the event make it clear Lin does this to make a point in favor of better treatment of her kind.
She may or may not be enjoying the circumstances, but at worst I read it as a "duty to perform" situation in Lin's perception, rather than MC abusing her trust. You could even argue (especially if this occurs with Lin's exhibition being high) that she actually wanted others in position of power to see the unusual bond she shares with the MC.
Especially considering Lin and the MC DO end up heavily influencing Cornwall's preconceptions about means of efficient slave training. Something that they probably wouldn't be able to achieve to the same degree through other means (or at all), even if you disregard porn logic.
Edit: Just to clarify - I wholly support your overall sentiment, but don't think it's applicable to this particular situation. And, as an aside, I think other people should write out their disagreements rather than dumping a "facepalm" on the post, especially considering your reaction is pretty understandable.