Ask your doctor to show you some references from medical journals showing valid evidence for high protein intake damaging kidneys in healthy people. I could almost guess with certainty that he will say something like "this is common knowledge," "Well [your name here], you see I've been a doctor for B years and I know these things," and expect him to get really upset.
I don't understand why some people believe people should be required to be treated by a liscensed doctor. This kind of stuff happens often, probably more often than malpractice is listed in most statistical data.