Not just the Greeks... Caesar said the Celts had hair like snakes. They skeered the bejeebus out of the Romans too, what, running around all naked, covered in woad, and freakishly long swords. The Celts are the one group of people that the Romans never truly conquered.

That an the whole lycanthropy thing... The Romans didn't much care for the idea of psychotic warriors with the rumoured powers to turn in to animals like bears or wolves. Just wasn't civilised.