Theft and other crimes seem to increase the more you remove or disrupt community. In other words, it's not about hostile communities, but the absence of community. In the absence of community, the default is hostility. Or, community is the establishment of non-hostility. Almost by definition. Community is people with common interests in a common location doing favors for each other and looking out for each other. When you have that, crime decreases.

There's also a generic version of the word "community" that people throw around, that can mean almost anything: a town (which isn't automatically a community)... gamers ("the gaming community")... "the Native American lesbian sportfishing enthusiast community"... and so on. I don't mean that.

Anyway, something "community-hostile" would therefore be anything that creates separation and alienation. Among other types of separation, there's separation in the spatial realm, such as through sheer distance (things are far apart), or through side effects of physical barriers that are part of the infrastructure, e.g. walls built to block traffic noise, or streets themselves, especially when wide and dangerous; or through other physical barriers that are more subtle such as the windows of your own car, through which you can see, yet you could easily drive right past your friend coming the other way without knowing it, whereas that would never happen if you were both walking or on a bike or scooter. Well, you say, I can just text my friend on my phone. Exactly, and now you're dependent on the phone maker, the carrier, Apple/Google, etc. for that communication to take place.