The other side thinks that HN's bias is liberal-SJW-Marxist etc. People notice most, and remember most, what they dislike. Some random examples—there are zillions like these:

https://news.ycombinator.com/item?id=21368961

https://news.ycombinator.com/item?id=20202305

https://news.ycombinator.com/item?id=15388778

https://news.ycombinator.com/item?id=16397133

Look closely and you'll find that ideological flamebait gets downvoted, flagged, and moderated on all sides here. The issue is the flames, not what color they burn.