I can't fully dispell it as a myth because I am convinced that most any kibble food is more harmful to our dogs than good.
When kibble is ingested it pulls moisture from the body and causes a mild state of dehydration. Where as feeding a raw diet which one would think is high protien the food is in its natural state and includes a great amount of water.
I have been reading up on kidney function lately for the heck of it since it seems to be a hot topic lately amoung people I know.
Ensuring your dog is getting enough moisture in its diet may just be enough to offset any damage that seems to be being blamed on high protien diets more so than the fact that it is a dry food.
Have you considered adding canned to your dogs kibble? It would increase the moisture content obviously thus not making many organs work that much harder to do their job.
As I said its only something I am just starting to learn about myself, however the more of this stuff I hear the happier I am that it doesn't pertain to my dogs being that they are all raw fed.
Courage is being scared to death and saddling up anyways. ~John Wayne