Whataboutism

Is "Whataboutism" a type of Red Herring?

Wouldn't redirecting an argument off the original by pointing to another instance unrelated to the first dilutes it by making it about more than just the specific original argument?

I guess you could say that. More often it's similar to Two Wrongs Don't Make a Right.
I.e., a political opponent is caught stealing. He/she responds: both sides cheat and steal.
Doesn't do the job. It's a deflection from the argument.
Great question.

Whaboutism is a modern English variation of the Latin Tu Quoque (ad hominem) argument.

As Dr. Bo defines it:

Ad Hominem (Tu quoque)
argumentum ad hominem tu quoque

(also known as: “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.

Logical Form:

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.
Example #1:

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.

Example #2:

Jimmy Swaggart argued strongly against sexual immorality, yet 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.

References:

Walton, D. (1998). Ad hominem arguments. University of Alabama Press.

I mostly agree with MCW - Whataboutism is usually a Tu Quoque fallacy, though depending on context it could also be Two Wrongs.

A type of ad hominem argument in which a person turns a charge back on his or her accuser:

Father: You should stop smoking. It is damaging to your health.
Son: Why should I listen to you? You started smoking when you were 15!

By itself, a tu quoque response to an accusation can never refute the accusation, which may or may not be provably correct.