(personal abuse/attacks, damning the source, a variety of the Ad Hominem)
A form of the Ad Homienm (which occurs when you dismiss what an opponent says because who they are), this fallacy takes it a step further by adding insult to the dismissal. Instead of attacking their position, you attack the person, even though the person making the claim is irrelevant to the claim itself.
This is effective because it forms associations in the minds of the audience. If someone wants to cut taxes, others may call them “stingy,” and this negative term becomes associated with the position regardless of any merit it may have. A very popular one in American politics is being called “Un-American,” which is ironic because it suggests the opponent is against basic freedoms like speech while also attempting to silence their opponent (or at least convince those listening that they should ignore him). Godwin’s law is a related to this and states that as online debates grow longer and more heated, it becomes more likely that someone will make a reference comparing an idea or a person to Hitler or Nazis – a comparison only appropriate when discussing the systematic genocide of a group of people.
A similar tactic is the strategy of “anticipatory name-calling” and involves saying something like, “Only an idiot would agree with her.” Those who use this strategy are purposely manipulating you in order to keep you from thinking about the issues. They aren’t actually assessing the viewpoint; they’re hoping that you are going to take their word for it in order to not be considered “an idiot” yourself.
We see many emotionally-loaded insults in the political season, and we must be careful to avoid dismissing a position because of the associations others want us to form.
Examples:
During the Senate confirmation hearings of Supreme Court Justice Clarence Thomas, Anita Hill accused him of sexual harassment. Thomas denied the accusation. . . . “During the hearings Hill, a graduate of Yale Law School and a tenured professor of law at Oklahoma State University, was labeled ‘a fantasizer,’ ‘a spurned woman,’ ‘an incompetent professional,’ and ‘a perjurer.’” (Jon Stratton, Critical Thinking for College Students. Rowman & Littlefield, 1999)
“Hilary Clinton is a liar and murderer, and if you agree with her, so are you.”
“You know what they say about a man with small hands…You can’t trust them.” Sen. Marco Rubio about Donald Trump in the 2016 Presidential Election. “Donald is not going to make America great. He’s going to make America orange!”
“‘The president sends out his attack dog often,’ said [Senator Henry] Reid. ‘That’s also known as Dick Cheney.’ . . . “Mr. Reid said he was not going to engage in a tit-for-tat with the vice president. ‘I’m not going to get into a name-calling match with somebody who has a 9 percent approval rating,’ Mr. Reid said.” (Carl Hulse and Jeff Zeleny, “Bush and Cheney Chide Democrats on Iraq Deadline.” The New York Times, April 25, 2007)