I agree this has always been a big issue with me as well, my RB terrier spent a week in a vet hospital after 2 Akita's (who were off leash) attacked him, mind you the owner yelled at me "don't worry they're friendly" just before they grabbed him. I was a teenager at the time and believed him, never again! My dogs, even Savannah, my aggressive one, walks fine on a leash, she'll even walk by another dog w/o problems if it's controlled(on leash) by it's owner, but if she's attacked I don't know that my training will stop her from defending herself. I've never had to test that and I'd rather not, which is why I was curious how other people handled this situation.