As I see it, Bennet was simply citing Levitt's book (which is old hat now), and he made it abundantly clear that the idea was abhorrent. The Dems have beaten Bush to a pulp over Katrina, and Rove to a pulp over Valerie Wilson/Plame, so Bennet just happens to be handy right now.
Anyway, Levitt is probably right, however, I'd amplify a bit and say that if you aborted all teen pregnancies, and all pregnancies of unwed woman on welfare, the crime rate would go down. Of course, we'd lose a lot of productive people too............Guess you'd have to do a cost/benefit analysis.