Who knows at the end of the day? But, if we can get people to stop and think we are half way there. It's always one to one if you change anything but its a link.
Pete Seeger and I were talking about this very same point and he always tells me of a young seminary with a sign against the war. Someone told him, "You are not going to change the world" And the young man said,"I'm trying to not let the world change me",or something like that. The point is if you believe what you are singing then keep going, no matter how out numbered you might think you are.
But to answer the question, yes I do think it has changed a few minds.