I don't know about racism as such but certainly Eurocentric diffusionism. People are, still, loath to admit that history has not been one long even progression from "primitive" to their own current way of life. If there are advanced ancient civilizations, it blows not just people's current sense of cultural and technological superiority, but also their eschatological hopes that the "progress of man" will continue into the future and liberate us from our problems. If we are not now at a peak, how's to be sure we aren't sliding into a trough? And this doesn't sit with the New Age mentality. For some folks, they may be happy to invite other races along, but not to give up on the notion of constant, eternal improvement. Solution? Find a way to contextualize the bright points in the past as still somehow a part of the presently unfolding future.