An appeal to pity attempts to persuade using emotion—specifically, sympathy—rather than evidence. Playing on the pity that someone feels for an individual or group can certainly affect what that person thinks about the group; this is a highly effective, and so quite common, fallacy.
This type of argument is fallacious because our emotional responses are not always a good guide to truth; emotions can cloud, rather than clarify, issues. We should base our beliefs upon reason, rather than on emotion, if we want our beliefs to be true.
Examples
Pro-life campaigners have recently adopted a strategy that capitalises on the strength of appeals to pity. By showing images of aborted foetuses, anti-abortion materials seek to disgust people, and so turn them against the practice of abortion.
A BBC News article, Jurors shown graphic 9/11 images, gives another clear example of an appeal to pity:
“A US jury has been shown graphic images of people burned to death in the 11 September 2001 attack on the Pentagon. The jurors will decide whether al-Qaeda plotter Zacarias Moussaoui should be executed or jailed for life… Prosecutors hope such emotional evidence will persuade the jury to opt for the death penalty.”