Al Mohler weighs in on 50 Shades here, in his article called 50 Shades of Shame.
Mohler reminds us that truth, beauty and goodness are inseparably joined together because they flow from and originate in God himself. He points out that pornography warps beauty by seeking to separate it from truth and goodness. That means that producing or partaking in pornography is an act of rebellion against God - willfully trying to separate what God has joined together. And make no mistake, Mohler clearly considers the 50 Shades books and movie pornography and recognizes in them an attempt to normalize and popularize graphic and abusive porn to a far wider audience.