I don't see a problem.

The problem was crime. Crime went down. Levitt made a hypothesis about why crime went down. Levitt proved his hypothesis.

Abortion reduces crime. There is no "problem" in his report. I don't really understand what you want him to change. It's up to politicians to use his data as they will.

He doesn't have an agenda. He isn't for or against abortion. He's just stating facts. He provides an alternate solution to using abortion, which is improving family life in some way for the poor. Economists don't impliment or legislate, they only observe and experiment.