HN has never been a site to shy away from political flamewars. You can look back through the various posts we have on China here where people rightfully claim the government in China has been responsible for various atrocities. Those threads fall along similar political lines and there's no real debate to be had, yet they still survive [1]. Hell, we can even talk about the recent threads on Trump [2] to see similar threads explode in popularity and make it through unflagged.
But we have a very obvious instance of something that all sides should be able to agree on, which is the feds picking up people off the streets without identification or recourse. This shouldn't even have political contention because both the left and the right should be able to agree it's a Bad Thing. Especially here on HN where there's a running trend of anything that involves censorship or rights being taken away [3] [4] [5] [6] gets massive amounts of traction but a story of very obvious government overreach ends up getting flagged.
This isn't to say that I think all topics are driven like this. As you've linked before, there are various discussions on police brutality made here on HN. But I've noticed those threads also go through significant periods of being flagged or pushed off the page until there's enough users to vouch for it or vote it up to bypass those flags. Which is to say I firmly believe stories nowadays are being flagged not on the basis of discussion but because of ideological reasons even if there are a few users using flags as it is intended. Otherwise why do those other stories explode in popularity considering they have the same levels of political flamebaiting?
[1] https://news.ycombinator.com/item?id=23739567
[2] https://news.ycombinator.com/item?id=23347155
[3] https://news.ycombinator.com/item?id=23223219
[4] https://news.ycombinator.com/item?id=23758547
