The relevant question is not who makes the argument, but whether the argument is valid. 1
Most debates on the internet are of "very low quality."2 They fail logically. They often devolve into abusive rants. This deters members from posting comments or articles. It destroys community. It also defeats the beauty of debate and dissent. As this forum encourages debate, we want our comments to be "above the fray." The ideas presented below are a small sampling of the discussion on ad hominem attacks that can be found on the web.
"An [ad hominem] argument is based on the failings of an adversary rather than on the merits of the case; [it is] a logical fallacy that involves a personal attack."3
"An argument that is ad hominem is one that has deviated from the claims being made and has instead focused on the person making the claims."4
"The abusive ad hominem is not just a case of directing abusive language toward another person. . . . The fallacy is committed when one engages in a personal attack as a means of ignoring, discrediting, or blunting the force of another's argument.
"Although some faulty arguers may call attention to distasteful features of their opponents in order to manipulate the responses of their audience, most abusers apparently believe that such characteristics actually provide good reasons for ignoring or discrediting the arguments of those who have them. Logically, of course, the fact that any of these characteristics might fit an opponent provides no reason to ignore or discredit his or her arguments or criticisms." 5
People's motives, their intelligence, their race, party affiliation, national origin, religion, gender, sexual orientation, employer, etc. is irrelevant to the debate. Commenting on someone's features whether true or not misdirects the audience through potent insults in an illogical attempt to discredit the ideas put forth. Just because someone is "stupid" does not mean the argument has no merit. That's a logical fallacy. By hurling insults, questioning the person's motives, or employer, you engage in ad hominem attacks.
But, this is only the most obvious form of ad hominem attacks. They can be subtle, too."[Another] manifestation of argumentum ad hominem is attacking a source of information -- for example, responding to a quotation from Richard Nixon on the subject of free trade with China by saying, "We all know Nixon was a liar and a cheat, so why should we believe anything he says?"
"Argumentum ad hominem also occurs when someone's arguments are discounted merely because they stand to benefit from the policy they advocate -- such as Bill Gates arguing against antitrust, rich people arguing for lower taxes, white people arguing against affirmative action, minorities arguing for affirmative action, etc. In all of these cases, the relevant question is not who makes the argument, but whether the argument is valid."6
Keeping the bolded part in mind makes it easy to recognize whether a comment is ad hominem or valid. Here are some more forms of argumentum ad hominem:
When you try to "persuade someone to accept a statement you make, by referring to that person's particular circumstances. For example:
Watch when making "you" statements. 'You' or 'your' is a tip-off you're about to personalize something.
'It is perfectly acceptable to kill animals for food. I hope you won't argue otherwise, given that you're quite happy to wear leather shoes.'
"This is known as circumstantial argumentum ad hominem. The fallacy can also be used as an excuse to reject a particular conclusion. For example:
'Of course you'd argue that positive discrimination is a bad thing. You're white.'
"This particular form of Argumentum ad Hominem, when you allege that someone is rationalizing a conclusion for selfish reasons, is also known as 'poisoning the well.'
It's not always invalid to refer to the circumstances of an individual who is making a claim. If someone is a known perjurer or liar, that fact will reduce their credibility as a witness. It won't, however, prove that their testimony is false in this case. It also won't alter the soundness of any logical arguments they may make."7
"[T]he truth of an assertion doesn't depend on the virtues of the person asserting it."8
San Jose State University characterizes the most frequent ad hominem appeals as attacks on: