If it's that bad, I would suggest therapy, Serenidad.
There is no way to avoid conflict other than to walk away, and not engage with the other person. You cannot stop strangers from lashing out but you can see it for what it is - someone who doesn't really affect your life other than at that one moment. If it's a stranger, why was he mad anyway? It's his problem.
Managing your fear is an inside job. I would suggest talking to a professional counselor.