Umberto Eco's "On Ugliness" contains an essay by some 16th century thinker about caricature, and what it means about our view of what is ugly (the author makes a relatively straightforward argument about something out of harmony and exaggerated helping us understand harmony, etc.) I don't think that necessarily applies to modern caricature, which can be both more subtle and more complex.
On the occasion of Osama bin Laden's death recently, Ralph Steadman created perhaps the best portrayal of OBL* that I've ever seen:
Look at the face: half of it is a giggling, ape-like horror, the other half an overly pious, stony religious zealot and ascetic fanatic. The body is misshapen, the head propped up by what is barely an arm. There is, of course, the blood spatter, alluding to but not wallowing in the terrorist's violent end.
Below, Steadman has clearly rendered bin Laden's legacy, the throne upon which his hunched body and heavy head squat. It is a throne made of the dead. Every suicide bomber inspired by a burning ideological fervor, every soldier sent justly or unjustly to war; it is the dead, innocent and not innocent alike, who are his sole contribution to history.
* - Steadman's portrait appeared in the New Humanist, an atheist publication. I found it on Andrew Sullivan's blog.