A man was left bleeding on a subway platform Tuesday evening after a mob of 10 unruly teenagers kicked him into a moving train — and the response from Boston progressives might be even more shocking than the attack itself. The victim, who was targeted during a dispute over a fare card at Back Bay Station, suffered a severe head laceration after being shoved into the train as it pulled into the station. A nurse who happened to witness the horrific scene rushed to help, keeping the bloodied man conscious while a transit police officer applied pressure to his wound....