i'd say this is a sort of false equivalency. stutterers stutter, so there's at least one reason to be wary of speaking in public: they don't want to stutter. non-stutterers don't stutter, but there could be other reasons for them not wanting to speak in public. i think a better question would be "why are some people afraid of speaking in public", and one answer could indeed be stuttering. but that's not the _only_ reason to be afraid.