In Salt Lake City, where I currently live, all I see are people complaining about homeless people and "suspicious people", who are _always_ people of color just walking down the street (who I've actually recognized occasionally).
Yeah, people call others out on this sort of casual racism, but it doesn't make it go away. It becomes a hotbed of these kinds of thoughts. When someone gets a bike stolen, you'll always see a comment like "The homeless problem here is out of control" and sometimes a comment with a picture of some random (again, person of color...) walking down the street from a Nest cam asking, "Did you see anyone like this? My bike was stolen too."
It's so odd to me to see all this on Nextdoor because I live a block away from a homeless shelter (one of the "gritty" parts of the city) and I can count only twice that I've had issues with homeless people or crime. I've lived here for almost six years now and I've never felt nearly as nervous or afraid as some of these Nextdoor users claim.
However, there is a ton of amusement from Nextdoor users, as well. The number of times I've seen people call each other rude because they used the word "fuck" in their post is extremely high, but that could be because I live in Utah haha.
In short, it's my experience that Nextdoor is filled with the type of person who calls the cops on their neighbors for no reason (like noise complaints). These users would really benefit from just getting to know their neighbors in real life.