I think
Ciaran8023's point was that there was no indication prior to taking the job that working for Kathleen would subject the MC to the same sort of sadism as the girls. Which is true in a literal sense. But IMHO, that's part of the point of the game: the MC's decision to work at the Club will have consequences, and not all of them will be under our direct control.
The game spends a great deal of effort establishing the morally dubious framework for the Club long before we work there - things like the MC ruminating on whether he's truly a good guy or merely lacked the opportunity to do bad, or the opportunity to exploit Rosalind simply because she agreed to it in a general sense. Kathleen drugging the MC is yet another aspect of that: the MC signed up for a dubious job, and it turns out not be what he thought it was. What does that say about the things the Carnations and the various house girls will be subjected to in the future?
To me, Kathleen's highly unethical railroading is a vital part of the story. It's
supposed to be beyond the pale precisely to highlight the way a lot of the other things we will have control over are just as dubious. I've said before that working for the Club is a Faustian bargain, and Kathleen's treatment of the MC is an early reminder that someday there will be a bill. I do not blame anyone who wants no part of that sort of thing and abandons the game as a result; I consider this game top notch, but it IS very much an acquired taste.
I do not, however, think Kathleen's abuse of the MC is sub-par writing. Distasteful as it is, I think it's very much the opposite.