Tenured Professor Confused By Negative Cube Roots?

I received this comment on a previous post.  I thought it important enough to make it a post.

“I routinely deal with college-level mathematics faculty that often have serious trouble with simple high-school mathematics. For example. I once had to explain that the domain of a cube root function is all reals and the faculty member (who has been granted tenure) look completely befuddled and wondered how this could be true. I was polite to say the least.”