During the Cultural Revolution, people accused of crimes had large sketches of themselves published in the daily rags and were made to wear white dunce caps and parade through town. Of course, during that time it was the librarians themselves who were thought to be the bad guys, not those being mean to them, more's the pity. Even now, the People's Daily continues to print perpetrators' photos very large. The next standard procedure is for everyone to shout a slogan at the criminal. In this case it may be something like: "Down with the use of mayonnaise to communicate displeasure!" or "Stop destructive condimentizing!"

As for why People's Daily was chosen to show Mom in the first place---simple. None of the others showed the Condiment Geezer in such a dramatic mug shot. Mom wanted everyone to be on the lookout, just in case.