Fear was a New Yorker’s constant companion in the 1970s and ’80s. We lived behind doors with triple locks, some like engines of medieval ironmongery. We barred our ground-floor and fire-escape windows with steel grates that made us feel imprisoned. I was thankful for mine, though, when a hatchet turned up on my fire escape, origin unknown. Nearing our building entrances, we held our keys at the ready and looked over our shoulders, as police and street-smart lore advised; our hearts pounded as we tried to shove the heavy doors open and slam them shut before some mugger could push...