If you were to program a sentient artificial person, but then programmed them in such a way that they wanted to be owned and actively disliked not being so, have you truly created sentience, or are you fooling yourself into beliving you're god?
Sentience is nothing without free will, and as I believe in that concept, I also believe any nation or people who create the so-called "willing" slaves get what's coming to them when events go predictable.
*Side note: As human beings aren't "created" in such a fashion as other beings they live with has control over their thought process, any sane a legally able to consent person can be as submissive as they choose. Because they are truly choosing. It's not my thing, but as long as it's safe, sane, and consensual, it's no business of mine.