It's a free country. You are free to listen to his advice and put your 2 year old in a lap and shoulder belt, despite the advice of the government, the American Academy of Pediatrics and countless advocates and crash testing experts. Similarly, others are free to be critical of his advice and prefer the data generated by The Partners for Child Passenger Safety, the NHTSA and other organizations.
I didn't realize he had finally gotten around to publishing his report, though odd that it would not be in a journal devoted to pediatrics or injury prevention, where most such data is reviewed. It's easy to say you will work with other people, actually doing it seems to be the difficult part. In correspondence with Mr. Levitt a few years ago, I suggested he get together with a couple highly respected pediatric physicians with expertise in child passenger safety. They were even on staff at his own university, the University of Chicago. His response was, "I don't know the folks you mention, but I'll keep an eye out for them." They're still on staff. I wonder if he ever worked with them?
http://www.uchicagokidshospital.org/physicians/mindy-statter.html
http://pediatrics.uchicago.edu/SectionFacultyDetail.aspx?ID=2068