Refuting someone's central point is often beside the point. Their central point may be a deliberate lie, a conscious shading of the truth, or a true but irrelevant statement, all meant to get you to buy something else entirely, the way the central point of a propaganda movie might be meaningless because the real goal is to portray the propagandist's allies/enemies in a positive/negative light.

Ad hominems and namecalling are an extremely effective way to reveal the truth, because they don't just strike at a single point, but the entire system of beliefs underpinning that point. People aren't robots and also don't need to be, our so-called biases are not programming errors and are there for reasons we don't fully appreciate.

In particular, namecalling - when the name is accurate - conveys a large amount of information about someone concisely.

Personal insults and how a person responds to insults can be extremely revelatory of deeper truths about the insulter and insultee's worldview and the material realities that inform that worldview. Pointing out that someone who demands material sacrifice of others is, say, incredibly fat and lazy, both points to their motivations for their position and their hypocrisy.

Ad hominems and namecalling - or generally, insults - often provoke emotional reactions from people, and emotional reactions are a valuable means of gauging the truth. Our "rational" mind is not honest and is often filled with bullshit that we convince ourselves to believe, while something that strikes at our emotions gets past that and hits us where we can't deny that something is true.

The pyramid of debate is stupid and not something that should be enforced as a matter of policy, because it inhibits the greater search for Truth.

Truth is God.

EDIT: This comment brings up a couple points which I want to address

First, that someone who (assuming they are not a conscious troll) believes in the Pyramid of Debate enough to argue with someone arguing against it doesn't believe in it enough to refrain from ad hominem. This also tells you something generally about the value of rationalized ideological claims when the rubber hits the road.

Second, that the ad hominem is a meaningful issue that, if it were true, would be relevant for people wanting to decide how they view what I have to say.