I'm not aware of too many crticisms of Freakonomics and its generally well regarded, but this particular claim has not stood up to scrutiny. Heres some reading if youre interested:

http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.600.6558

https://uncertaintyblog.com/2013/08/15/fooled-again-pinker-puts-a-nail-in-the-coffin-of-the-freakonomics-crime-theory/comment-page-1/

http://www.economist.com/node/5246700