I get the seniment but I disagree. I have a full set of Canon L series primes and L series zooms as well as a growing m4/3 system (pus some MF film stuff, panoramic cameras, housings etc). They are both useful and important in different situations. I'd agree that primes are better if you want to LEARN photography and improve at the maximum rate, but if you actually know what you're doing????
I find that Ken Rockwell often tries to make others look like they don't know what they're talking about to cover up for the fact that he doesn't know what he's talking about.