The level of violence is definitely down over the past 15 years. Regardless, they're the Westboro fringe, and you can't fix crazy.
I don't think you can call the Boston union guys a fringe element when you have guys like Bears worshipping at their feet.
Perhaps slashing tires is an extreme that few stoop to anymore, but the tone of the threats, foul language and otherwise obnoxious behavior exhibited on their picket lines are more or less the norm. Certainly, it matches with what I've seen on picket lines and SEIU demonstrations in downtown Chicago, and it's not too far off from what we've seen in the airline industry.