springmom, if I still had the old family ranch down below Cuero, I'd actively hope that killing the sows would cause the death of the piglets. The simplest reason is that no rancher wants his pasture to look like a bunch of drunk backhoe operators ran amok. It's far worse if you're a farmer; the crop damage from feral hogs can make the difference in one's quality of life itsownself. Oh, and I about forgot: If you're in the sheep/goat business, feral hogs will kill and eat lambs and kids.
From the standpoint of hunting ethics, sure, I can see mixed emotions about shooting a sow. And that's why doe-hunters look for a "barren doe": No fawn. But it's really a lot better to think of feral hogs as edible cockroaches--and cockroaches are a lot easier to deal with. We've made a game out of killing feral hogs, but they're still varmints, not game animals in the accepted sense. Again, think "cockroaches".
If those piglets were anywhere near weaned, the only future hazard they really face is reduced protection from coyotes, and I'm cheering for the coyotes.
Art