Many places have all of the single-family homes also owned by corporations. I think the problems you are concerned with here are predominantly increasing financialization of the economy and increasing wealth inequality rather than anything to do with zoning changes.
> what I'm arguing for is a working middle class that should have access to living in the city with a modest back yard
If housing has gotten so expensive that the "working middle class" has to live somewhere else and commute in, the way to attack that is to increase the stock of available housing, not continue to sharply restrict it.
> crusade against SFHs has a distinctly classist, anti-middle-class
To the contrary, relaxing zoning requirements most strongly benefits people who are less wealthy and currently end up overspending on housing or getting priced out.
> what I'm arguing for is a working middle class that should have access to living in the city with a modest back yard
If housing has gotten so expensive that the "working middle class" has to live somewhere else and commute in, the way to attack that is to increase the stock of available housing, not continue to sharply restrict it.
> crusade against SFHs has a distinctly classist, anti-middle-class
To the contrary, relaxing zoning requirements most strongly benefits people who are less wealthy and currently end up overspending on housing or getting priced out.