[facepalm]

I must admit I can not really relate. What about somebody who can not FizzBuzz, but claims they can code? Most whiteboard interviews I had were not much harder than FizzBuzz. I was asked to implement Quicksort once, but they gave me the specification, some time and a sheet of paper.

Why would somebody for whom it is easy consider to hire somebody who can not do a seemingly simple thing?

I can understand if somebody has anxiety issues. Then maybe you can negotiate something else, homework project or coding on site for 30 minutes. But odds are you'll discuss stuff with your colleagues on a whiteboard, too.