I live in Seattle, and I can tell you from the few times I've been on NextDoor, even in a blue city like ours, I was surprised at how racist people still are, albeit subtly.
Not my direct neighbors, but definitely someone a few streets over. I actually thought that their house was vacant until I received the letter.
Because all that will do is create high school style drama about who's more correct.
But if you want to get into an eternal hate match between your neighbors full of passive aggressive backstabbing, there is no quicker way than to call them out on their causal racism.