Mike that is not my position and I apologize if I am not conveying that properly. My position is that white-boarding in front of people you just met for some people will not convey that they can do it. Because they can become distracted by perceiving that they are a spectacle and their every move is under a microscope. Many developers have been in such a situation and walk away from the situation permanently affected by it. It only take one bad interviewer to criticize your every move to make a developer analyze their every move in future interviews. But that does not mean in their natural and comfortable environment they would have such an issue. It is why I prefer to look at code they produced in that natural and comfortable environment.

Stage fright is an excellent point. So excellent that I wonder why nobody else made it before, and instead went for BS reasons like "I need a debugger". Maybe due to stage fright...?

I think the two are linked, some developers feel secure that a compiler / debugger will catch the inevitable simple mistakes that we all make. Not having one in front of an audience makes it that much worse. A lot of those that protest would feel a lot more comfortable in front of people if they knew they had a net to catch the simple errors they make before they show off their code and that's the core of my position on the subject, code test guarantee that these otherwise competent individuals will look incompetent and once they do, it's hard to minimize that experience in the interviewers mind, Steve Jobs called it the bozo bit and once it is flipped it's pretty much flipped for good. The fact that they look incompetent on the whiteboard is such a strong reaction, that it outweighs compensation factors like looking at code already written, in a more conducive environment.