We have a 70 kg neutered Italian Mastiff. If I take him for a walk, he is ALWAYS on leash. But to be completely honest, the poor guy hardly ever makes it out unless it is up the hill behind our house.
With all the loose dogs around it is just too dangerous. Dogs on leash feel very vulnerable when approached by, usually multiple dogs at once in La Manzanilla.
It has crossed my mind in those situations, to just unleash him, and let him, and I with a big stick, have a Louisville slugger, take care of business. That wouldn't end well for anyone.
Back in my more naive days, we have been approached by what I am sure is the dog in question. Always a tense situation.