As a whole, I've found photography is a very petty niche, populated with many self-important prima donnas. I think it's really easy to make something that appears to be a "good picture", so practically everyone feels like a photographic expert whose authority on the niche should be respected. This is amplified in photography because it's very hard to make a living in it, and a lot of people feel jealous and resentful to the few who are able to do so.

There's also a common impulse in all niches to hate on whoever is popular and attracting a lot of newbies. Rockwell certainly does that.

While there are certainly things that even relatively-inexperienced photographers can find to disagree with Rockwell about, there is no doubt that his web site is useful and informative, especially as introductory material.