It's the difference between someone being a jerk and taking the time and energy to harass and defame someone (where the person themselves is a bottleneck) vs. running an unsupervised agent to carpet bomb the target.

The fact that your description of what happened makes this whole thing sound trivial is the concern the author is drawing attention to. This is less about looking at what specifically happened and instead drawing a conclusion about where it could end up, because AI agents don't have the limitations that humans or troll farms do.