Probably the second most common logical fallacy plaguing American discourse, after the ad hominem fallacy, is the non sequitur fallacy. Examples are everywhere:
Palin Critic: “Former governor Palin is a poor public speaker.”
Palin Fan: “Well, President Obama is a socialist.”
The Palin Fan’s comment doesn’t address the argument made by the Palin Critic. It’s isn’t responsive. Stated formally,
A is B
C is D
Therefore A is not B
“Non sequitur” is Latin for “it does not follow.” We are conditioned by advertising to give such obviously false arguments consideration. Advertising along the lines of “Buy a Rolex watch and everyone will respect you” is a classic non sequitur. Respect doesn’t follow from purchasing consumer goods. But I think hearing it so often weakens one’s ability to recognize the fallacy.
Hundreds of thousands of advertisements doesn’t make the fallacy any less false.
The fallacy isn’t always used out of ignorance. It can also be an effective if unprincipled attempt to shift the subject. If a unscrupulous debater can’t respond to an argument, he or she may attempt to shift the issue by raising a different point. Like the use of an ad hominem fallacy, it’s an implied admission that the speaker can’t address the real issue; it’s conceding an argument.
The non sequitur is frequently combined with the ad hominem fallacy.
Palin Critic: “Former governor Palin is a poor public speaker.”
Palin Fan: “You’re a woman-hater.”
The way to handle a non sequitur fallacy is the same as the technique for the ad hominem fallacy, if it is used in a discussion or debate. Point out that the response is an attempt to shift the issue, and not responsive to the real issue at all. You can even ask if the person raising the non sequitur is conceding the main point. Drag the discussion back to the issue and away from the digression, no matter how inflammatory or personal the digression. If you permit the issue to be shifted, you are playing the other person’s game.
Wickersham's Conscience 