I can see that, and perhaps my experience has just been unlucky. I missed usenet by a few years.
Someone making point with a couple of paragraphs.
Commenter takes one sentence or point to shred, maybe it was a weak example or poorly phrased, to invalidate the whole.
repeat. After a few rounds it's becoming clear they're intentionally avoiding the main point.
Have I just committed the cardinal sin of being wrong on the internet? ;)