I remember reading something about sex offenders not using porn as much as the general public a long time ago.
And here it is.
In 1970 President Nixon’s Commission on Obscenity and Pornography did a study on the effects of pornography on the common person. They found that pornography is not only harmless, but is also a healthy part of growing up. 
The study showed that the majority of sexual offenders had been exposed to less pornography than average while growing up.
...and also...
In 1967, the Danish parliament took all restrictions off the sale of written and pictorial erotica. Danish researchers found the rate of sex crimes in Denmark dramatically decreased, finding that prospective sex offenders could relieve their tendencies by looking at pornography instead of engaging in the act itself
http://www.oregonlive.com/forums/hil....ssf?artid=124