That's really disgusting behavior on the part of the DSCC. Pretty far beyond the pale of what I would consider even remotely acceptable. I should hope that whomever came up with this line of attack gets the axe shortly, although of course the higher-ups who approved it won't.
Also typical of standard practice in Massachusetts. People are so unused to running close elections they have no idea what plays and does among people who don't viscerally hate their opponent. Tom Allen saw this in Maine where he nuked himself with his negative attacks, and the Democrats are busy self-destructing in Massachusetts. First Capuano's violence comments and now this.