To quote Dr. Bernstein:

Because the survival rate of diabetics on dialysis is so much lower than that of nondiabetics, some dialysis centers are now using low carbohydrate, high-protein diets for their diabetic patients.

In summary: Diabetic nephropathy does not appear if blood sugar is kept normal. Dietary protein does not cause diabetic nephropathy, but can possibly (still uncertain) slightly accelerate the process once there has been major, irreversible kidney damage. Dietary protein has no substantial effect upon the GFR of healthy kidneys, certainly not in comparison to the GFR increase caused by elevated blood sugar levels.*

The May 1996 Journal of the American Medical Association published a summary of fifty-six studies demonstrating that in nondiabetics increased protein consumption actually lowered blood pressure.