Appeal to Emotion
The Fallacy
Manipulating an emotional response in place of a valid or compelling argument.
Why it's wrong
Appeals to emotion include appeals to fear, envy, hatred, pity, pride, and more. It's important to note that sometimes a logically coherent argument may inspire emotion or have an emotional aspect, but the problem and fallacy occurs when emotion is used instead of a logical argument, or to obscure the fact that no compelling rational reason exists for one's position.
Example
Luke didn't want to eat his sheep's brains with chopped liver and brussel sprouts, but his father told him to think about the poor, starving children in a third world country who weren't fortunate enough to have any food at all.