Going out in public with a large unleashed dog is a bit like going out in public with a semi-auto that has the mag out and the slide locked back with a range flag hanging out of it and then pointing it at folks as you walk around.
You and anyone with gun experience will be able to tell that it's not dangerous, but that doesn't mean it's OK. It's still going to scare people, and even the people who know it's really not dangerous may still be uncomfortable with you pointing it at them or others.
Besides, do you know how to tell when people are lying (usually unintentionally) about their pets (or kids)?
They start their sentence with: "My pet/kid would never..."
Animals are very complex, it is not possible to predict their behavior with 100% accuracy, nor is it possible to have 100% control over them.