An ad Hominem is a general category of fallacies in which a claim or argument is rejected based on some irrelevant fact about the person making the claim or argument. The demonic version of this fallacy involves two steps, the first of which distinguishes the demonic from the normal ad hominem.
First, the target of the ad hominem is demonized. As noted in the previous essay on the subject, demonizing is portraying the target as evil, corrupt, dangerous or threatening. This can be done in the usual three ways: selective demonizing, hyperbolic demonizing or fictional demonizing. Selective demonizing is when some true negative fact about the target is focused on to the exclusion of other facts about the target. Hyperbolic demonizing involves greatly exaggerating a negative fact about the target. Fictional demonizing is simply lying about the target. Second, this attack is taken to be evidence against the claim or argument in question.
The demonic ad hominem has the following form:
Premise 1. Person A makes claim X.
Premise 2. Person B demonizes person A.
Conclusion: Therefore, A’s claim is false (or A’s argument fails).
The reason why the demonic ad hominem is a fallacy is that demonizing a person has no bearing on the truth of a claim or the quality of an argument. In addition to the logical error, a demonic ad hominem also suffers from the fact that demonizing, by definition, involves deception. At the very least, demonizing involves taking facts out of context and often involves outright falsehoods.
A demonic ad hominem can have considerable psychological force since demonizing typically goes beyond the usual attacks in a non-demonic ad hominem and thus can trigger strong emotions. A common tactic is to demonize the target using stereotypes the audience already accepts and by appealing to their biases, fears and prejudices. Such an audience will be inclined to accept the demonization as true and their emotional response can lead them to accept the fallacious reasoning.
There are two main defenses against demonizing. One is to be aware of the ad hominem aspect of the fallacy. Even if the demonizing claims were true, the reasoning would still be flawed: true but irrelevant negative claims about a person, no matter how terrible, do not disprove a claim or argument. The other is to be critical about negative claims and only accept them if they are adequately supported by evidence.
Some of Trump’s defenders have used this fallacy to attack the Democrats in congress and those testifying before them. For example, when Lt. Colonel Vindman testified, he was demonized with assertions of dual loyalty and some even seemed to go so far as to cast him as a spy. The intent was to discredit his claims by lying about him. As another example, some of my Trump supporting friends on Facebook posted images featuring the false claim Schiff used taxpayer money to settle a sexual harassment case involving a 19-year old man. The intent was that Schiff’s claims and arguments should be dismissed because of this (false) claim. While some people do believe these sorts of claims, even those who do not can be influenced by them when they are repeated often enough. Laying aside the matter of logic, there is also the moral concern about such attacks and the damage they can do. Those who get demonized all too often become targets of harassment and even death threats. There is also the interesting point that if Trump is truly in the right and should no be impeached, then the truth should suffice. It must be noted that the use of these tactics does not prove that Trump is guilty of impeachable offenses, but it does suggest that he does not have the truth on his side.