Users flagged it, most likely because the post is a personal attack (a pretty ugly one actually) which is not in the spirit of this site as expressed in its guidelines: https://news.ycombinator.com/newsguidelines.html.

We try to avoid posts that are personal attacks, not necessarily because we owe celebrities better, but because this kind of internet denunciation degrades the community, even if it also makes some good points. I think that's probably why users flagged it.

Trying to prevent the community from degrading is more important than any individual post, as it's the container that supports good discussion in the first place. The container is fragile. It's more fragile than it seems, because much of the work to prevent it from falling apart isn't visible.

Posts that feature indignation over information are always bad for curious conversation. When the indignation is directed against an individual, that's a multiplier of badness, because it brings out worse in others.