1. "You're getting angry. Thererefore, there must be some merits to the argument you are attacking."
Ridiculous for transparently obvious reasons. The emotional tenor of a debater has no bearing on the correctness or incorrectness of his or her argument. Yet, this tactic is frequently employed in all seriousness, usually by people who have no better counterargument to put forward.
Now, for any particular person, there may be some statistical correlation between one's emotional tenor and one's beliefs about the merits of the argument under discussion. For example, when a position with which I disagree has some merits or subtlety, then I can take some intellectual pleasure in figuring out why it's still wrong. In such cases, my prose tends to remain fairly neutral in tone --- see, for example, my discussion of the death penalty versus war.
However, when an argument strikes me as having no redeeming features whatsoever, then I transmogrify into a volcanic fountain of vitriol and contempt. See, for example, my post about Jonah Goldberg.
In such situations, there are several possibilities. Either the person making the argument knows that it's ridiculous, or he does not. In the former case, he's trying to deceive his audience by making the argument. In the latter case, either he hasn't thought very hard about the argument he's making, which means he's consciously wasting his audience's time, or he's too stupid to see how flimsy his argument is. Now, if he's deceiving his audience, or wasting his audience's time, then I claim that anger (or at least contempt) is, in fact, the proper response to his behavior. He's inflicting harm on his audience, and some altruistic punishment is in order. Only in the last case --- i.e., he's too stupid to see the flaws in his argument --- does he deserve any sympathy. And frankly, when that stupidity is paired with arrogance, as it so frequently is, it's really hard to muster sympathy even in that case.
Now, once again, none of this really demonstrates anything about the merits of the argument under discussion. I could be furious, but mistaken. I just thought it might be worth explaining when and why I, personally, tend to display anger in my own writing when an argument's absolute nonsense.
2. "You just claimed that I possess [bad trait X]. Therefore, you are engaging in ad hominem and your argument is wrong."
Also ridiculous for transparently obvious reasons. People who use this argument unadorned do not understand what ad hominem means --- it denotes an argument wherein one makes the following (invalid) chain of inference:
- Person P has the property X.
- X is bad.
- Therefore, the argument A advanced by P is invalid.
Notice that ad hominem is not a synonym for "insult". If you make a charge of ad hominem, then it does not suffice to show that someone has been insulted. It is necessary to show that the insult was used as evidence that the argument is unsound.
However, I often see the above argument confused with the following one:
- Person P advanced argument A.
- Argument A is so ridiculous that it could only be advanced by someone having property X.
- Therefore, P has the property X.
Now, this chain of argument is perfectly valid. In most cases, it does not take a terribly discerning eye to distinguish this argument from the prior one. If you attack the person first, and use that attack to back up a conclusion about the argument, you probably have argumentum ad hominem. If you attack the argument first, and use it to back up a conclusion about the person's character, then you probably have the latter argument. Nevertheless, many people fail to distinguish the two, and thereby reveal themselves to be idiots.
Exercise for the reader: Which one is the last sentence of the previous paragraph?
A final note: Use of either of the above argumentative tactics demonstrates mere intellectual bankruptcy. To use both of them at once requires a special, additional helping of argumentative incompetence --- because, of course, the first argument is actually a form of genuine ad hominem.
p.s. In case you're curious as to what prompted this, all of the above has been a way of mining some usefulness from this random babbling (which came up on Technorati links here) by extracting general rules from a specific instance of intellectual bankruptcy. You can, perhaps, amuse yourself by counting how many times this writer (who claims to have some training in philosophy) makes the above errors, but you're probably better off not clicking the link.