Earlier quoted context omitted.
tptacek nailed it with regards to it being historically racial, but I've also seen, to your point, animosity towards anything that isn't a "traditional" or nuclear family. Fear of the different and unknown is a powerful motivator of the people who bring these complaints. Also animosity towards poverty and the belief or perception of material increases in crime and/or traffic. (property owner, many units, yimby, have…
The whole race thing is a red herring. Pretty much every "racist" law outside of the former confederacy was written with the Irish in mind and last I checked they were just as white (technically whiter if you want to hair split) as the wasps who championed those laws. Those people back then were trying use government force to make it harder for people to live in ways they didn't like in the via regulation all the sam…
There are political cartoons drawn by fascists from the 1920s that attempt to stave off accusations of racism by pointing out that they include Italians (then show Mussolini as a racist caricature of a black man), as if Italians aren't widely considered white.
If you look at how the British and later Americans talked about the Irish "people" or "race", you'll note shocking similarities to how they talked about Africans, Native Americans, Asians of all stripes, etc etc. Explicit skin color rarely came up.
Racism, especially old timey racism, is all about "how do I define my group as 'good' and everybody else as so bad that I can treat them worse?"