What externalities? I hear this ridiculous point all the time, but have absolutely no evidence of it being a real problem.

Yes, there are bad guests occasionally. But there are also bad tenants occasionally—and the former is a hell of a lot easier to deal with quickly.

AirBnB house has positive externalities, and is much more desirable to live next to than multifamily, at least in the type of town I live in.

This is why my land owning neighbors love me and are happy with the direction the neighborhood is changing into.