--Don't mess with the elderly in this city. They are not easy targets. A guy found that out when he tried to steal an old woman's purse at the Downtown Crossing T stop. On Wednesday night, Christopher Linehan, 29, of Dorchester, tried to snatch the purse of the unidentified 79-year-old woman. Neither party would let go of the purse, so Linehan tried dragging the woman to one of the black turnstiles. Good Samaritans started blocking......