That is indeed a very odd situation. I can't imagine anyone thinking it's ok to just let their dog bark non-stop like that while they are standing right there and are perfectly capable of doing something about it. Is it always the same person?
I know confronting them sucks but I also agree that it would be the best approach - at least at first. Maybe your boyfriend could do it? I'm no good at confrontation myself, so I'll admit it's definitely something I would pass along if I could
Best of luck. Hope it gets solved.