Thing is, a lab goes beserk, people go..oh, it's a lab

...my two boys respond with their much deeper barks, in a different situation (not my vet's office thank goodness, they love rotts and my boys) people react differntly, so I would rather my boys be held to a higher standard...fair or not. So, I want to understand the behavior, and how best to deal with it...and at one and two, they are being butt head punks.