In his appearance last week on Radio Boston, Dan Grabauskas didn't discuss the issue of violence on the T. No one else asked him about it, either. But he has a lot to do now that a 15-year-old named Tiara Amarante documented the perils of riding the 23 bus. People riding the 23 are living in fear of thugs who pack heat, fight and intimidate riders on a daily basis. Amarante is a freshman at......