It's easy to look at incidents like this from the comfort of one's armchair and condemn the perpetrator in cases like this. What I know about the lobster industry wouldn't fit on the head of a pin compared to Dave's knowledge from living and working in that part of the world.
But the few lobstermen I had the opportunity to talk to at length in Maine and particularly on PEI made it obvious this is not an easy or secure living. If I correctly understood what I was told, on PEI (don't know about Maine) the licenses that are issued are for a certain area along the island's coast. You can fish in your designated area but not in another one.
Then within that area, each lobsterman has specific places that they fish. This is not anything legal, it's just a territorial assignment that has evolved over time. Some of these spots are handed down from father to son or shared within a family. When I asked what would happen if someone set pots in another person's spot, the answer was always the same: we cut them loose.
It's easy and natural for people outside the industry to say, "Oh, I'd never do that," or "They should be punished for that, it's illegal," or whatever. But I believe it's impossible to understand the challenges, pressures, and concerns of someone who works in an industry--- any industry--- unless you work in it, too.
If my ability to support my family, pay my bills, and keep gas in the car depended on the lobsters I was able to catch in my licensed area and "traditional" spots and someone else started setting pots in my spots and threatening my ability to suport my family, I sure as hell would be cutting pot lines and even sinking boats if it came to a choice between that or letting my family down. It may not be legal, but it's life and if they can do it without being caught and persecuted, more power to them.
Vandalism is another matter, as is damaging property to settle grudges based on something other than "poaching." But protecting your abiilty to make a living, anything goes in my book.