Oakland, in the Jerry Brown years, practiced an unofficial policy of what might be called “community cleansing.” This is not to be confused with “ethnic cleansing,” the horrific activity in parts of, say, Eastern Europe or Central Africa where whole ethnic populations are violently and bloodily removed, either through exile or actual genocide. No, Mr. Brown’s “community cleansing” policies were far more genteel, involving little violence (though some—that’s what the whole Oakland Riders police scandal was about) and targeting not whole ethnic groups, but rather portions of the population that were considered as being “undesirables.” Part of this involved harassment,...