It's common sense that the board is more dangerous. Obviously the person riding it is mostly at fault, but the board exacerbates the problem. I'm not saying ban SUPs, but how some people act on a SUP is very dangerous/negligent. I live on the east coast and I've seen many experienced riders lose their SUP in small surf around people. They are more dangerous than the alternative, no question. They are simply harder to control, and have more weight, surface area, and force behind them, making the potential results much worse.
If you have one of those things and you ride it at a beach break when no one else is out, I think that's great. Sounds like fun. If you take it out around people, and you've ever lost the board around people, you are the problem.
Longboards do a GREAT job of riding the east coast surf and are significantly less dangerous than your standard SUP. Personally, I have no trouble getting a fish type shortboard in the water multiple times a week when I want to. Much easier to control these types of boards and be safe when around people. However, there are still plenty of people on these boards who can't control them. But, they aren't as dangerous as losing a SUP because they weigh less so there is less force behind them, and they have less surface area to hit you with. Not to mention they are harder to lose. See the difference? Not saying its OK to paddle out a shortboard in a crowded lineup when you don't have a clue either....
Sounds like you need to move. The breaks in my area are never crowded enough to make SUPs a big issue. Longboards are not an alternative to SUPs. It is silly and pointless to paddle out on a log in 1ft mush.