I think the author is being too harsh here. Democratic rule in these urban toilets is usually a symptom of the problem, not the cause.
I would make the case that urban life in general is highly dysfunctional, and breeds the kind of cultural rot that turns these cities into Democratic strongholds.
It is a sort of chicken-or-the-egg kind of thing. One reason cities tend to be dysfunctional and degenerate is that they attract the dysfunctional and degenerate migrant-- the down-and-outer, the drifter, the criminal looking for new turf--and those opportunists who prey upon them.
Cities are crowds of strangers, providing the atomization that allows predators to flourish in anonymity.
The Democrat machines recognize this, and join the hunt, casting their welfare bait among the would-be victims, who then become their lawful prey.