I know Ori Hofmekler (Warrior Diet) is against whey isolate, as is Dr. Mercola. I had always thought the protein is damaging on the kidneys thing was a myth, but Hofmekler actually does mention it:
"The whey minerals are the best in the world.
What‟s interesting about these minerals including the organic minerals that basically they are water soluble. What makes them water soluble is the fat in milk everybody wants to remove. The phospholipids help with delivery of these cations, positive charged ion minerals like calcium and prevent it from being non-water soluble calcium which is very adverse and dangerous to your kidney."
Dr. Mercola's comments on isolate:
"All whey protein isolates are devoid of nutritional co-factors including alkalizing minerals, naturally occurring vitamins, and lipids, which are lost in the processing... This renders them deficient and overly acidifying. Unlike whole protein food concentrates which does not acidify your body due to it's alkalinizing minerals, whey protein isolate are over acidifying.
Whey isolate can be a serious liability.
If chronically consumed in large amounts (such as with bodybuilders or athletes) without alkalizing foods, it can acidify your body and over time may lead to metabolic acidosis with consequences that include waste of muscle and bone tissues, total metabolic shut down, and increased vulnerability to degenerative disease.
Many cheap whey protein isolates are produced from acid cheese; they're byproducts of acid processing, which is a cheap way to separate whey from the curd. Most of these whey products are rated below pet foods because of the inferior quality of the protein, which is actually more of a nitrogen waste product than one that will produce health benefits that are mentioned in the featured study.
Additionally once the fat has been removed from whey protein isolate, you lose some of the most important components of its immunological properties, such as phospholipids, phosphatidylserine and CLA. All of the IgG immunoglobulins, which are an excellent source of glutamine and glutamylcysteine, are also bound to the fat globule, and therefore lost in the processing of whey isolates."