My first, instinctive, response is that high protein diets were fine for home sapiens for some 50,000 odd years and beyond, and previous homo-species had the same diet before that.
I'm also pretty sceptical re: 'foods that come with the protein', ala milk w/whey shakes, the saturated fats that come with lots of red meat, the unsaturated that come with fish etc. Isolating the effect of any 'high protein' diet is going to be difficult; you can't honestly point the finger at the protein and exclude everything that comes along with it, relative to the protein source.
From the Livestrong page, "Dietary changes in the carbohydrate to protein ratio produce changes in glucose regulation, as shown by Donald K. Layman and colleagues published in "Human Nutrition and Metabolism" 2003. Therefore, high-protein diets influence insulin levels within the body."
This sentence is just stupid.
Obviously that has nothing to do with you. But that as nearly as many holes as a recent photo-comparison argument that was attempted recently.
Going back to my undergrad and research days, low carb diets increase insulin sensitivity. You're much more likely to get a 'sugar rush' than you will on a high-carb diet. High-carb diets have clearly and thoroughly been shown to induce insulin resistance (welcome to type 2 diabetes etc). High protein, by definition must be low carb, low(er) fat.
This is the first time I've ever heard someone say that high-protein (absolute and in terms of diet proportion) is bad due to impact upon insulin regulation.
Frankly, I think they're taking a few things out of context, and are also ignoring 50k years of anecdotal evidence regarding high-protein diets. They're also not touching total caloric intake at all; type 2 diabetes is almost impossible to develop for those eating sub-maintenance.
I understand the concept they're driving at, but I think there's some major flaws in the argument and conclusion.