Don't be confrontational. I've been accosted by people driving by "scrubland" that obviously didn't belong to anybody, wasn't being used by anybody and he had no intention of actually getting out of his vehicle and walking around (except to yell at me) until he saw the dog.

Just say "sorry" get the dog on a leash and leave. You won't win any argument here. And better, he won't be there tomorrow if you decide to go again. Pick your battles. I have been aggressively chased by teenagers on motorbikes and quad bikes. My dog can outrun them. My story will be if the police show up is that they were harrassing me (white middleaged female) and my dog was being protective. (He only wants to run with them, but they don't know that). I'll take my chances if the police show up. Then again, I have some Qatari friends who might be willing to help me out.

You will not win in a "written" rules situation because there are none. Go when there are few or no other people. Know your animal (mine chases cars or people who are running - including joggers - again, he just wants to run with them, but they don't know that and he's not attractive for that reason in the west). I do not inflict my dog on other people either here or in North America.

Please pick up after your dog - I know there's a lot of human faeces around but you can pick up after your own dog.