You're also making assumptions, but about a real person. They never once spoke about the servant but you involved him anyway. Why are you so aggressive over what someone thinks the servant's sex attitude's like anyway? What quality do you attach to being a bottom exactly that you get so triggered at the thought? Maybe you're the one projecting your personal experiences.
I'm all about not imposing your fantasy onto someone, not stereotyping or objectifying them, but read the fucking tags girl, and also read the room. A story about a master and a servant, more than half the chapters of which involve fan-servicey smut scenes or dirty thoughts and barely any focus on character depth beyond that. Is it that unbelievable to express personal expectations related to the sex it portrays? They're not even unrealistic.
You're the only prissy baby here whining over hypotheticals. It's okay to have different expectations and experience a story differently. It's actually you who doesn't have the right to dictate that for someone.

:/ My. It is hurting my head when the seme-like is not the seme.