Over the years, think my attitude has changed and would now generally support the move to public areas being on leash for dogs, as much for dog safety as humans.
Stan is only off lead in fenced off dog fields, some are OK but others are just mud baths. Quite a few near us close in winter due to waterlogging, also it can be hard to book places in 'after work' hours, many close once it's dark - for obvious reasons.
At one point we thought Stan would return on call reliably in low distraction areas, or so it seemed. He then buggered off down a steep embankment next to the canal chasing rabbits/rats (we think) and would not come back at all. Muggins had to scale the north face of the Eiger to corner him and nearly ended up in the canal, his wagging tail suggested this was the best game ever. Never off lead in public areas since then.
He was also always muzzled when out when we first got him, but it made people far more wary (not necessarily a bad thing) but he seemed more outwardly aggressive when muzzled.
Our previous dog, when younger, was only aggressive with other dogs /people when on the lead. Suspect she felt handicapped/cornered being stuck, chained to a human anchor with the agility of a dump truck. Off lead she was confident of being able to escape with sheer speed and agility. Even then, only off lead where there was lots of space and no 'unknown' dogs.