I've been dealing with the same situation almost everyday. MAXIMUS is always on leash. He doesn't appreciate other dogs, big or small, getting near me. It freaks me out every time a little dog comes running towards us. He could very well hurt them, severely. I always have to yell at them to 'go home' or 'go away.'
I thought of a spray bottle of water. But, I don't want to have to get that close. Maybe a water gun? MAXIMUS has been doing so well ignoring other dogs on our walks. But, what is he to do when they come at him?