“Fifty Shades of Grey” is voluntary female behavior. When it is not voluntary, it does not enjoy the protection of the law in our society, and no religion operating in our society gets a pass on beating women based on the religion’s scriptures.
My own view is that some acts are objectively wrong, regardless of "consent." Put them in the "depraved heart" category of crime. Whether it's done to the "consenting" Anastasia Steele or the "consenting" Atika Latifi or Umm Bint-Anybody, it's reckless endangerment maybe, assault for sure.
There are some things you shouldn't legally be able to consent to. Among these: (forcible) rape, slavery, sodomy, torture, assault, murder.