Part of me feels like that sanitized Israel-Palestine community exists to deflect criticism of their Zionism elsewhere on the instance.

I think that's partly true. I also think it also exists as a counterweight to soothe the internal conflict of liberal zionists; on one hand they are larping pro human rights etc., on the other hand they use authoritarian measures to shut down any discussion about the middle east that doesn't fit their "both-sides" milquetoast agenda. By creating a dedicated space they can 1.) banish the palestine conflict and the associated tension/injustice from their main communities by redirecting them to c/nah_ost where it can be safely ignored and 2.) they can save their liberal self-image by going "see, we allow for debate and dissenting opinions!".