Should i be worried?

well..yeah thats not enough evidence to think they neglect or abuse him. Lots of GOOD dog owners yell at their dogs because they dont know other training methods like positive reinforcement. You dont know if these people have taken their BC to any obedience school since they keep to themselves. I'd let this one go...why bother people who seem like they wouldnt handle the stress of animal police visiting in a good way. Theres lots of types of people...outgoing, quiet, stressed, happy, busy, caring, too caring, etc...just because these people are different from you doesnt mean they're bad or treat the dog bad. This dog sounds like he's a heck of a lot better off than in a overcrowded, high kill shelter. And if you really want to make a difference for dogs who do need it, you'd be great in shelter volunteering!