Yes your barber was correct and all the guys with really coarse tough beards either grew full beards or tried shaving and bled to death. Therefore only the guys with the full beards could pass on their genes for tough beards so your probably related to one of those full beard guys and should grow one too. Har har

Count yourself lucky that barber didn't give you a shave. he was probably incompetent and lacking confidence. You are correct that at one time everyone had to use a straight if they shaved so that's the rest of the story.