Most of Mr. Saletans article hinges on his definition of the word "separate", which he defines in paragraph two. This may be an honest mistake - I don't know anything about Mr. Saletan. But my guess is that he wanted to paint the SD abortion law as ridiculous and lawmakers as idiots. If you think of the term "separate" as "distinct", it conveys the true meaning of the law. In otherwords, if Suzy who is 7 months pregnant with Johnny (already named after the dad) is killed in a car accident but the emergency medics are able to save Johnny, we can see that there are two distinct lives here.
Rather than this kind of disingenuous twisting of words to set the stage for a pro-abortion sermon, I would rather see an honest debate on the subject. There are two basic camps, the pro- and anti-abortion. As of the Roe v. Wade decision, judicial fiat has established that there is pretty much no restriction on abortion. The People did not vote, congress did not debate, the states didn't have any say, and abortion was unilaterally declared legal, with almost no limits. If abortion were put to a vote, we would almost certainly see some restriction. As in South Dakota, where the legislature has passed this law. I believe the SD law is a positive step toward taking into account the will of the people, many of which still consider life to be God-given and not something that should be subject to someone else's 'choice'.