True enough - in those regions, red hair is a sufficiently rare occurrence to be associated with some sort of dark magic or curse. Which is also very likely the reason that southern Britons originally formed a dislike for their northern cousins with the fiery locks.
These "beliefs" have been around for much longer than the knowledge of Neanderthal hair color.
Surely our Cro-Magnon forebearers who competed with the Neanderthals for hunting grounds and occasionally mated with them knew what color their hair was by simple observation. The suggestion (not my own) that I communicated was that anti-ginger prejudice is that old and persists with its reasons forgotten.