"As the use of porn increases, the rate of sex crimes goes down"

This is a perfect application of "Correlation does not imply causation". It's very likely that over time (during which internet porn has skyrocketed and made consumption frictionless) the awareness for supporting victims of sexual assault as also gone up.. from completely unrelated trends like rises in feminism and an overall decrease in crime over the last 15 years.

Source 1995: http://www.fbi.gov/filelink.html?file=/ucr/Cius_97/95CRIME/9... 2008: http://www.fbi.gov/ucr/cius2008/data/table_25.html