I'm in the same boat. 95% of dog owners in my neighborhood walk their dogs off leash. Not even unable to read their own dogs body language but also ignoring me when I tell them to get their dog or even not let it approach further.
If anything, they react with "he's friendly", "he just wants to play" and stuff like that.
Given the fact my boy has some AmStaff in the mix, if my boy reacts, they are trigger happy to insult me and put all the blame on me...even though my dog is leashed and theirs is not in an area with strong leash laws.
I called my regulatory agency twice already. The problem is that the are I walk my dog daily is a HUGE nature preserve area and you basically can walk there for hours without meeting a single soul, sometimes it's the unofficial dog park of my city though.
Last time I called the regulatory agency they apparently did sent people to control the area...so I heard from some lady I met walking her dog off leash...apparently they caught her off leash the week before and told her, if that would happen again, she had to pay a fee...
yeah, just warning people that "next time" they will get punished seems to work out perfectly fine.