I'm not sure if you're asking a rhetorical question, but I believe it's because (whether right or wrong) the linked thread is perceived as belonging to the "redpilled, conservative, traditional masculinity" subculture.
>The RAND American Life Panel and the Ipsos KnowledgePanel are nationally representative probability-based survey panels of adults in the United States
Well, I was commenting on why I think the thread was flagged, not whether I think it should be. Also, the main content of an HN thread is typically in the comments, not the link.
I disagree. The link is at best one data point, when the comments provide a whole body of content. Of course, the bulk of the comments should be productive, then, in order for the thread to be productive.
While HN is not great on politics, I'm not aware of any decently large (or small!) community that is.