A similar term, attributed much earlier to Lenin, is "useful idiots."
Both terms refer to the lack of critical thinking among very large segments of the population. Because of this deficiency, these benighted souls rely on past patterns of behavior to inform their actions. They are also easily swayed by group-think and the rhetoric of manipulators. Spin doctors know that these people are beyond reason and logic, and can very effectively control them by playing to their puerile desires.
Ad hominem arguments are personal attacks. It works by implying that the messenger is tainted, therefore the message is tainted and can be ignored. It is a smear tactic.
"An ad hominem argument, also known as argumentum ad hominem (Latin: "argument to the man" [or] "argument against the man") consists of replying to an argument or factual claim by attacking ... a characteristic or belief of the person making the argument or claim, rather than by addressing the substance of the argument or producing evidence against the claim.
"The process of proving or disproving the claim is thereby subverted, and the argumentum ad hominem works to change the subject."
(Wikipedia and other references here)
A perfect example of "ad hominem abusive" was perpetrated on me last March 3rd at the Manteca City Council meeting. During a review of that so-called hearing, a comment was made that after I finished presenting the documented evidence the entire public discussion shifted immediately "from facts to feelings.” Indeed, the O. Rex was on a mission to absolve the city from any of its responsibilities (such as enforcing its own ordinances) by smearing me with the broadest, blackest brush possible. My theatrical neighbor was given the floor for a little redneck standup comedy - again at my expense - without refuting a single charge against her. The entire charade comprised an astonishingly successful ad hominem attack.
In true committee fashion, the "useful idiots" occupying the council seats and the chairs where city department heads are supposed to sit, went along with the hijack. If any of them (especially the Director of Community Development) had a thought, it was only, "How do I keep my ass out of this sling?
Despite the oxymoronic ethics of attorneys, I am certainly expecting more attempts at character assassination from the defendants and opposing counsel.
I can only hope that a court of competent jurisdiction, as a "tryer of facts," does indeed examine and weigh the factual evidence and not rely on, or be swayed by, the ad hominem fallacy.