Frankly, he's right about UI design and programming being completely different disciplines, and he's absolutely right in saying that being a good programmer produces zero likelihood of being a good UI designer.
\r\n\r\nIs the 'construction worker' analogy off? Yeah. I'd say the difference is more that of a structural engineer and an architect. But in the face of the dismissiveness most free software folks show toward usability and UI design, I don't blame him for being a little over-the-top in his characterization.