Two things:
1. Bill Bennet seems to have had a logical slip-up. He is trying to make two separate points, and somehow they ended up blended together. The one that he concludes with is that "these far-out, far-reaching, extensive extrapolations are tricky." Which is a pretty good point. The book Freakonomics does not prove conclusively that abortion rights leads to lower levels of crime, and one could argue that the data from which the conclusion was drawn are too limited for any strong statement.
The other point, which Bennet tries to blend into the first point, is, "if you were to abort all black babies, the crime rate would go down, even though it would be reprehensible." This example seems to be supporting an implied, but not stated, argument that, "just because abortions lower crime rates, doesn't mean that they are morally justified." Completely different argument, and also a pretty decent one, despite the way he put it!
I agree with the argument he is trying to make, but not his method of making it. His comment is not a satirical comment--it's
reductio ad absurdum. What is "absurd" in his mind is the idea of aborting all black babies. The implied argument, after all, is that "you can't do something reprehensible just to reduce crime."
What is *not* absurd in his mind, what is implied as being a perfectly clear fact in his argument, is the fact that aborting black babies would lead to a lower crime rate. What he says, quite plainly, is this: "I know it's true that if your sole purpose was to reduce crime, you could abort every black baby in this country, and your crime rate would go down."
That's not the way you phrase a hypothetical argument. The way you would phrase it is: "let's say, one day, statisticians figured out that aborting all black babies would lead to a reduction in crime." There's a big big difference.
In his defense, I think the fact is right, actually. If you were to abort a large portion of babies from lower income families, crime would be reduced. Blacks are disproportionately represented in the poor income bracket; therefore, aborting black babies would lead to reductions in crime. If this is what he meant, and maybe it was, he should have been *much* more careful in how he said it. His statement can easily be misconstrued as meaning that blacks are inherently more likely to grow up to be criminals.
2. Freakonomics is a great read! I recommend it to everyone. The argument regarding the link between abortion and crime isn't iron-clad, but it's still pretty darn convincing. In addition, it's very very entertaining--not dry at all. His interest is interesting statistics, not a political agenda. For examples of his type of analyses, try out this great bit from the book, regarding high-income baby names:
http://slate.msn.com/id/2116505/