Going strictly on the wording of the debate question and insufficient data contained therein, the murderer may have caught because of a face on a milk carton. Who knows, right? In any event, one has to turn only to himself and ask, "If I or a loved one were missing, would I disagree with the face of that person plastered on everything possible?".
The pictures are a good idea because even if someone never actually sees the missing child, they would know if they were to ever cross their paths or notice something suspicious. Justice can be slow but it's better to be actively doing something to try and find a missing child instead of no one knowing what they look like.
Getting the faces of kids out into the community is a great idea. Although justice was slow in coming for Etan Patz, the guy WAS eventually caught. And while this particular case took a long time, other kids have been helped in that time as well. You can't just say this isn't a success because of one case, especially when that case was solved eventually.
There are many positive and helpful things that have resulted from the missing child movement. Advancements in search processes and involving the public in the search for missing children has helped return some children. Since the movement began, people are more careful about security for their own children. But the milk carton campaign did not help return Patz or any other children.