Incest I'll leave alone. Lot's of biological reasons for banning that, or at least procreation through incest. Though in this day and age, consensual incest, say between brother and sister or even between father and adult daughter (or mother and adult son) for purely recreational purposes maybe should be acceptable.
But as for a Dom/sub relationship, can it be false imprisonment if the sub consents? What if she had a safeword, affording her the option to terminate her "imprisonment" whenever she feels threatened? And is it abuse if the sub invites it? And what about sex while in bondage? Can that be considered rape, even though the sub consents to it?
No, I think we need to keep the government, and especially the church (any church) out of our bedrooms/dungeons. As long as a relationship is between two consenting adults, with no real harm to anyone, it's nobody else's business.