If you are talking about stories only, written language, he can write whatever he wants.
You should read some Marquis De Sade, 18th century hardcore rape and torture.
http://en.wikipedia.org/wiki/Marquis_de_Sade
Or listen to some of the lyrics of Slipknot.
Or watch some films like Cannibal Holocaust.
I personally am not into that stuff but people write about it and i suppose they will continue to write about it.