Since nobody would ever object to it, protecting against child abuse gets used as a wedge. As the article points out, the way this story ends is with this very

Since nobody would ever object to it, protecting against child abuse gets used as a wedge. As the article points out, the way this story ends is with this very backdoor getting used for other things besides preventing child abuse: anything the government asks Apple to give them. It's an almost inevitable consequence of creating a backdoor in the first place, which is why you have to have a zero-tolerance policy against it.