Why all pro Palestinian posts in Hacker News are flagged?
My guess is because it violates the HN Guidelines.
"Off-Topic: Most stories about politics, or crime, or sports, or celebrities, unless they're evidence of some interesting new phenomenon. Videos of pratfalls or disasters, or cute animal pictures. If they'd cover it on TV news, it's probably off-topic. "
https://news.ycombinator.com/newsguidelines.html
You should probably check out the FAQ, too:
https://news.ycombinator.com/item?id=38691198 This post got flagged despite not being offtopic. An encyclopedia being accused of siding with perpetrators of genocide is not a small thing. Remember the coverage of Ukraine war here.