argumentum ad hominem tu quoque
(also known as: appeal to hypocrisy, “you too” fallacy, hypocrisy, personal inconsistency)
Description: Claiming the argument is flawed by pointing out that the one making the argument is not acting consistently with the claims of the argument.
Person 1 is claiming that Y is true, but person 1 is acting as if Y is not true.
Therefore, Y must not be true.
Helga: You should not be eating that... it has been scientifically proven that eating fat burgers are no good for your health.
Hugh: You eat fat burgers all the time so that can’t be true.
Explanation: It doesn’t matter (to the truth claim of the argument at least) if Helga follows her own advice or not. While it might appear that the reason she does not follow her own advice is that she doesn’t believe it’s true, it could also be that those fat burgers are just too damn irresistible.
Jimmy Swaggart argued strongly against sexual immorality, yet while married, he has had several affairs with prostitutes; therefore, sexual immorality is acceptable.
Explanation: The fact Jimmy Swaggart likes to play a round of bedroom golf with some local entrepreneurial ladies, is not evidence for sexual immorality in general, only that he is sexually immoral.
Exception: If Jimbo insisted that his actions were in line with sexual morality, then it would be a very germane part of the argument.
Tip: Again, admit when your lack of self-control or willpower has nothing to do with the truth claim of the proposition. The following is what I remember my dad telling me about smoking (he smoked about four packs a day since he was 14).
Bo, never be a stupid a--hole like me and start smoking. It is a disgusting habit that I know will eventually kill me. If you never start, you will never miss it.
My dad died at age 69 -- of lung cancer. I never touched a cigarette in my life and never plan to touch one.