I've seen people ask the best way to report black people to the cops so they'll be kept from driving through "our safe neighborhood." It's so full of dog whistles my neighbors dogs bark when I open the app.
The only reason NextDoor is freaking out is because they know there's enough of that sort of material to really cause a mass exodus if it ever escaped the neighborhoods it's posted in.
That said...it's...a weird issue, to be sure. NextDoor tried to encourage an expectation of privacy but like...who actually expects that? Really. Anyone with a credit card matching the address they key in can get in. It's not the post card only thing any more.
I could easily change my billing address on my credit card, sign up for some neighborhood on the west coast, and then change my CC address back. Done.
NextDoor has done nothing to actually secure the neighborhood, so it's not like it means anything to say this to the customers. If anything, the neighborhood members could possibly sue NextDoor for overstating the privacy of their posts.
I guess the conclusion is: I'm not just throwing my hands up and saying, "Oh well it's online no privacy!" I'm more saying this is probably the absolute worst hill to choose to fight that battle on.