"Name calling is abusive or insulting language referring to a person or group, a verbal abuse.
The technique is most frequently employed ...in an attempt to negatively impact [an] opponent.
Name calling is a cognitive bias and a technique to promote propaganda.
Propagandists use the name-calling technique to incite fears or arouse positive prejudices with the intent that invoked fear (based on fearmongering tactics) or trust will encourage those that read, see or hear propaganda to construct a negative opinion, in respect to the former, or a positive opinion, with respect to the latter, about a person, group, or set of beliefs or ideas that the propagandist would wish the recipients to believe.
The method is intended to provoke conclusions and actions about a matter apart from an impartial examinations of the facts of the matter. When this tactic is used instead of an argument, name-calling is thus a substitute for rational, fact-based arguments against an idea or belief, based upon its own merits, and becomes an argumentum ad hominem.
At one end of the “never acceptable” range were “dishonest” (23%) and “corrupt” (24%). The public did not consider these names as offensive as others. At the other end, the top two “never acceptable” names – “numbnuts” (84%) and “jerk” (83%)
Gratuitous verbal abuse or "name-calling" itself is not an argumentum ad hominem or a logical fallacy.
The [logical] fallacy only occurs if personal attacks are employed in the stead of an argument to devalue an argument by attacking the speaker...
However, because a statement can be countered by multiple lines of reasoning, any name-calling relating to the mental faculties of the opponent is typically a case of argumentum ad hominem.
For example, ad hominem attacks would include saying the opponent is slow-witted, uneducated, too drunk to think clearly, or needs more sleep for correct judgment. "X's argument is invalid because X's analogy is false, there are differences between a republic and a democracy. But then again, X is idiotically ignorant" is gratuitously abusive but is not a fallacy because X's argument is actually addressed directly in the opening statement. "X is idiotically ignorant" is not a fallacy of itself. It is an argument that X doesn't know the difference between a republic and a democracy. But, the implication is that the opponent is too "idiotically ignorant" to think clearly, about anything.
An example of a direct ad hominem fallacy would be "X is idiotically ignorant [of politics], so why should we listen to him now?"