There's a lot of thinking relating to design on the web that doesn't have anything to do with code. Big picture strategy, overall user experience, effective use of visual language, and a litany of other things are complex areas deserving the attention of the designer.
We hire smart people to think about design, and other smart people to worry about code. This works very well.
Some purists believe you need to distill a pursuit down to its base elements, in order to consider yourself a master. While I appreciate the noble sentiment behind such notions, I believe it to be flawed. For example, I knew one fellow in art school who insisted on grinding down pigment and making his own paint before he'd touch brush to canvas. The unfortunate part for him, was that all the time he put into this kept him from doing the important part: making great paintings.
A good interaction designer needs to understand the limitations and possibilities of code. They don't need to be a master of it, so long as they work with someone who does.
A reasonable comparison would be Peter Jackson. He makes great movies, because he hires individuals with great talent in their respective fields; then he concentrates on the "movie making" part. My hunch is that if he were to stitch together each garment for the film, he'd never finish a production.
The irony in my arguments is that they are, in ways, as impassioned as Andy's. Nevertheless, I believe mine have less manipulative ends in mind. My perspective on this one is largely informed by some of the (many) unsuccessful applicants who wish to work at our agency. The vast majority try to do everything, and therefore excel at nothing; I'd love to see more of those folks focus, and become really good at one thing.