Jamie Oliver's a pretty visible target if some doctors wanted to get attention by attacking an iconic promoter of the learn-to-cook-fresh-food-at-home trend.
But if some publicity hound doctors like grab headlines with stunts, he kind of opened himself up for it by putting out a fast(er) food cookbook. Anyone who publishes a "Meals in Minutes" book where the food is gourmet-ish is not going to have the healthiest recipes, unless most of the stuff that winds up on the plate is actually raw.
Even so it seems as if they were cherry picking.
Consider the original source of the unhealthy claim, the Physicians Committee for Responsible Medicine. They are primarily an advocacy group pushing a pro-vegan, anti-animal research agenda. I would view their proclamations on the unhealthiness of Mr. Oliver's food as a publicity stunt, guaranteed to generate buzz on the web.