This is SOP for dem's. Here in Massachusetts it is common knowledge that the union thugs always harass the opposition, destroy signs and bully sign holders. That is why there hasn't been a legit election in MA for decades.
Quick anecdote: When Romney ran against Ted Kennedy for the Senate (1994?) there was a debate held at Fanuel Hall in Boston. During the 6:00pm ABC news there was a plug for the local channel 5 news at 11. Evidently there was a clash between supporters outside the hall. A bunch of union guys were bused in by the Dem's and they started harassing the Romney people and trashing the Romney supporters signs. Police were called in. "Details at 11." But when the 11 o'clock news came on there was no mention. Go figure.