Appeal to Hypocrisy

This is also known as Tu quoque.

This is the fallacy where what one person says something that appears out of character according to another person's view of him, therefore it is rejected by that other person.

Examples

TV Pundit A says that illegal immigration is a very bad thing. It turns out that he is married to a Mexican woman and he therefore has Hispanic children. (Most illegal migrants are Mexicans.) Therefore his wife is not of Mexican heritage.

Freddy the career criminal went into a store and came out with a bag of stuff. A suspicious cop demanded to see a receipt, so Freddy showed it to him. Faced with the contradiction that a criminal would engage in legal commerce, the cop refused to believe his own eyes.

A father who is a smoker tells his kids that smoking is unhealthy. Everyone points out that he is a smoker. Therefore the kids reject his opinion, and decide smoking is not unhealthy.

Weaknesses

The unimaginitive mind is often befuddled and vexed by contradictions. He cannot understand how two seemingly contradicting propositions can be valid. However his psychological state of frustration has no impact on reality and facts. Contradictions are commonplace, and apparent contradictions often conceal complex relationships.

Therefore you can point out to the arguer that he needs to:

• Question his assumptions.
• Accept and investigate complexity.
• Recognize that appearances are misleading.