Hate me if you want, but why do I have to get them to like me to have sex? I am keeping them as a slave. Last time I checked consent was never there in the first place, and now I have to get it?

you have a point 

You don't need their consent when they're invading your dungeon but suddenly do once you capture them.

Honesty, I spam the sex button until they accept. I also spam "how are you?" in the chat options over and over until they worship my character. <3