I personally don't think Stallman is entirely right, but I think he articulates his ideas quite clearly. Anyone who doesn't listen to him because he has a beard or whatever clearly doesn't care about the truth in the first place.
That's not to say that it's not worth convincing people who don't care about the truth, but rather that you need different kinds of people willing to play different kinds of roles in order to create social change. Just because Stallman isn't going to be the guy who convinces the masses doesn't mean that what he's doing (in general) isn't vital to the movement.