I would also have to intervene, I couldn't let that go by.
There was an older man 'training' one of his ESS's on the Chase. The dog was ignoring his whistles and signals. As I walked up the path, I got mine close to me because the one dog was on the path and didn't look 'right' at all, very anxious. The dog on the path was a JRT and I soon saw whey he was looking so wary. The man was thrashing the spaniel with a thin leather lead and after he put on the said lead, proceeded to belt the dog around the face. I told him to stop hurting his dog and he went into a rant about 'don't you tell me how to train dogs...' His last comment was, 'I've tried everything else'. So what was he going to do? Keep going until he nearly killed his dog - because that was the only other option left to him on that train of thought
I'm quite sure he didn't pay any attention to me but at least it might make him stop and think before he acts like that again (at least in front of people).
If the dog warden is no help then I would walk up to him and ask him if you can have a chat. It's not age, it's knowledge and perspective.