Hilzoy expresses it eloquently:
It’s easy, in the midst of a political campaign, to forget that the people involved are, after all, people. Some of them — Sarah Palin, for instance — place themselves under a media spotlight of their own free will. Others — her daughter, for instance — wind up there through no fault of their own. Imagine yourself in her position: there you are, seventeen years old, pregnant, unmarried. Maybe you understand what happened and why; and maybe your parents and friends do as well. But zillions of bloggers and reporters and pundits are about to make the most personal details of your life into a political issue, and they don’t understand it at all. And yet, despite that, they are about to use you and your unborn child to score points on one another, without any regard whatsoever for you and your actual situation.
[…] As far as I’m concerned, it’s fair game to consider Sarah Palin’s statements about her daughter’s decision, and to compare them to her own views about abortion. That’s a story about whether or not Sarah Palin sticks to her beliefs when they affect her own family, not about her daughter. But it is not fair game to use her daughter, or any of her kids, as pawns in a political argument. To my mind, this extends to using her daughter as evidence that abstinence-only education doesn’t work: presumably, no one thinks that it works 100% of the time, and that’s the only claim to which this one counterexample could possibly be relevant. (That’s why God created large-scale studies.) Likewise, I think that arguing about whether Sarah Palin is a good mother is out of line: we have no idea at all what arrangements she and her husband have made for child care, how their relationship works, and so forth. Assuming that Sarah Palin would have to be her children’s primary caregiver is just sexist.
Those who are using this issue to base their voting decision are revealing a greater affinity with tabloid-inspired mob mentality than with real life as well as displaying a severe lack of understanding of the skills required to be a good leader.