Personal Attack (ad hominem)

==Definition==
A person commits the fallacy of ad hominem when they attack not their opponent's argument but their opponent themselves (i.e. the attack is not on an argument but on the person who makes it).
:Pattern:
:A is a bad person.
:Therefore A’s argument must be bad.
==Example==
This ad against Proposition 8, "And She's the California Constitution," commits the fallacy of personal attack.
 
This ad, modeled on the popular Mac vs. PC ads, features two men and a woman. The first man young and hip: he is dressed in jeans, a t-shirt and a hoodie. "Hello, I'm No on Proposition 8," he says. The second man -- "Yes on Prop. 8" -- is middle-aged and overweight; he is dressed in an ill-fitting brown suit, and his tie isn't long enough to make it over his belly and to his belt. The woman is beautiful, perfect; she introduces herself as "The California Constitution." YES is represented as something of a buffoon: He is ignorant, crude and sexist. He ogles CALIFORNIA. When NO says to leave her alone, that "she's perfect the way she is," YES responds, "She'd be even better with a little discrimination in her (if you know what I mean)." YES then struts over toward CALIFORNIA, telling NO to "watch and learn." When CALIFORNIA asks YES what he's into, he responds, "Deciding what's appropriate for everyone else; government interference in personal lives; judgement." (He punctuates this with a little low "umpf" punch). The ad doesn't really engage any argument made by supporters of Prop. 8; rather, it implies that they all, like YES, are desperately un-hip, ignorant, and prejudiced (comitting still another fallacy, hasty generalization). The ad doesn't counter any claim made by supporters of Prop. 8; rather, it ridicules them and dismisses them. In the words of CALIFORNIA: "You should go play with something other than the California Constitution."
==Other examples==
This ad for Republican Presidential nominee John McCain, "Ayers," commits a related fallacy, "guilt by association," or "poisoning the well," 
:Definition
:The arguer attacks not their opponent's argument, or even their opponent, but their opponent's friends.
:Pattern:
:A's friends are bad people.
:Therefore A’s argument must be bad.
The ad opens with menacing, "time-bomb" music and black-and-white mug-shot-type images, including one of Democratic Presidential nominee Barack Obama. The narrator begins: "Barack Obama and domestic terrorist Bill Ayers. Friends." She then recites the evidence of this friendship: "They've worked together for years," she says, adding: "Ayers and Obama ran a radical education foundation together." Having established their association, the narrator then goes on to list Ayers (alleged?) crimes: "We know that Bill Ayers ran the violent left-wing terrorist group called Weather Underground. We know Ayer's wife was on the FBI's 'Ten Most Wanted List.' We know they bombed the Capitol, the Pentagon, a judge's home." The implication is that, by virtue of his friendship with Ayers, Obama is guilty -- or "guilty enough" -- of Ayers' crimes. If Ayers is dangerous, then Obama, we are supposed to conclude, is, too. The narrator delivers the verdict: "Barack Obama: too risky for America." In this ad, McCain doesn't engage Obama's arguments; rather, he attacks Obama by attacking his friends. We are not given any reason to believe that Obama has proposed any policy that would be dangerous, only that his friends are dangerous. We are supposed to conclude that means that Obama, too, is dangerous and "therefore" nothing he could propose need be examined on the merits.
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Another ad for John McCain, "Acorn," commits the same fallacy.