DS: Can dogs distinguish between human accents? (See details)?

Our dog came from a rescue centre in Liverpool, and he had a bad time before he was taken there. A while after we got him we were sitting on a bench with him and a guy came past who was obviously from Liverpool who had a strong Scouse accent and our dog went crazy at him. I was just wondering if it could have been he recognised the accent and associated it with something bad, or whether there was something else about the guy he didn't like so it was just a coincidence.