People are biased toward underestimating how much legitimate disagreement there is in any large, distributed population sample—which HN is. Probably we're hard-wired to evaluate the world by local conditions around us, and most of us are surrounded by people who see things similarly to how we do. Then we come online, bump into views that are harsh outliers in our world, and poof: an astroturfer under every bed and a spy in every closet.
This is so close to a universal mechanism that we have a rule about it in https://news.ycombinator.com/newsguidelines.html:
"Please don't post insinuations about astroturfing, shilling, brigading, foreign agents and the like. It degrades discussion and is usually mistaken. If you're worried about abuse, email hn@ycombinator.com and we'll look at the data."
Please note: this is not to say that abuse doesn't exist. But the overwhelming majority of such insinuations are imaginary, so in investigating real abuse we need concrete evidence to go on—something, anything. The presence of opposing views on an internet forum does not clear that bar—it is evidence of nothing but that the topic is divisive.
Piles of past explanation are at https://hn.algolia.com/?sort=byDate&dateRange=all&type=comme...