Saletan's argument only makes sense if you already assume that abortion is morally neutral. Legally, he may be correct, but the legal status of abortion doesn't decide its morality. Saletan's argument shifts from a legal basis to moral basis, and back again, at the convenience of the point.

• From a moral basis, Palin's argument is clear: abortion is immoral for everyone, period. It therefore doesn't matter what the daughter's under-age opinion is, or whether the daughter needs her mother's consent. However, current law allows abortion. On the other hand, it also allows parental consent. So, anyone who opposes abortion morally can't stop abortion outright, but that same legal system allows the opponent to use other laws to thwart abortion. The law permits abortion, but allows opponents to stop it.
• That's part of the problem with abortion itself, and especially a problem with how we discuss it. The current law on abortion was not set by popular consent, after a thorough debate. It was imposed by Roe v. Wade, using suspicious legal reasoning. No one, except perhaps legal fanatics, would argue that a Supreme Court decides morality as well as law. The law is just an instrument in the larger conflict of morality, and all sides exploit the law when its to their advantage. The law is the ball that we kick forward when we try to promote our view of morality. And so we're left with pro-abortion laws that were imposed by judicial fiat, but anti-abortion laws that were passed through legislatures.

Pro-lifers (like me) believe that Roe v. Wade unfairly exploited the authority of law to steal the public decision about abortion in the first place. You can't then complain when we also exploit the law to promote our values.