That's one possible interpretation. Another possible one is people don't want to see HN become Trump, Trump, Trump and maybe some other story like the rest of the news.

It just pushes everything to the middle. If you think logically about it, since there are few if any conservative posts, it makes sense that flagging appears to be conservative because the majority of posts that need to be flagged are liberal. If suddenly there were lots of conservative posts, the liberal flaggers would appear.

If you want evidence of this consider comments. Conservative comments are often quickly downvoted.