What this analogy says is that people don't want other people living at high density near them. This is expected, since those other people are going to be poor and often dark skinned. Needless to say "other people are pollution, yuck" is not a good argument for zoning.

I think the argument would be much stronger if it just stopped at poor. While Im sure that type of racist exists, I have never met someone who would object to a rich dark doctor moving in next door. To the extent I encounter racism, it almost always follows the logic that dark = poor = crime & dysfunction

Nah bro. You didn't call me a racist for this? WTF?