I never heard this myth, and I had a very liberal education up until college.
Keeley gives plenty of examples and I've run into more than a few young brains full of mush that buy into this stuff. An extension is the theory that Europe was a peaceful matriarchy of humans living like bonobos and worshiping the Mother Goddess until those evil patriarchy-loving warriors came along and imposed a male-centered religion on them. Not much evidence for either but they both make for a good story that meshes well with leftist and feminist thought (or what passes for thought).