When Decarlos Brown, Jr., fatally pierced 23-year-old Iryna Zarutska’s throat on a Charlotte, NC, commuter train last August, the horror made global news. Last week’s  fatal shoving  of 76-year-old Ross Falzone down a flight of Manhattan subway steps commands equal outrage for what it says about the city’s steep decline in transit safety. For decades, New York succeeded in keeping its transit system safe. Recently, we’ve just given up on doing it.   For any transit rider, watching the video of Falzone in the seconds before his murder conjures the same emotions video of Brown’s random attack on Zarutska evoked.  We see Falzone, a retired teacher, confidently walking down Chelsea’s 18th Street toward the subway steps, backpack slung over his shoulders.   He feels no danger; he appears to be reading a piece of paper.…