How is rape porn any different than watching violent movies? Both depict illegal acts. Why is one okay, but the other not? The act of rape is illegal, why isn't that enough?
Movies of that nature would face the same uproar, and indeed have (the idea of 'snuff films')
You watch boring movies.
Some are even torture porn with explicitly detailed and violent rape scenes[2]. These are also planned to be banned if I am not mistaken.[3]
[1] http://en.wikipedia.org/wiki/Splatter_film [2] http://blogs.wsj.com/speakeasy/2010/03/15/a-serbian-film-sho... [3.a] http://www.huffingtonpost.co.uk/2012/07/11/torture-porn-atti... [3.b] http://www.theweek.co.uk/film/50537/uk-film-censor-get-tough...