The president of the United States should not lower himself to such childishness.
Having said that, any person who has decided to enter the public realm is fair game for criticism, so criticism of this manufactured figurehead is entirely warranted. Going after a kid just because a person hates their father, isn't.
Rather than criticize this kid directly, such criticism should be aimed at the media that created her and then congratulated itself for the effectiveness of their choice by making her person of the year. It is all very cynical and represents the way our media has shifted from reporting on the news to creating it in order to serve an agenda.
I find our agenda driven media to be a far worse problem right now than global warming.