a fairy tale of modern times!

It is a sort of common believe that protein and also calcium put a strain on the kidneys and may overload their filtering capacity, impair their health and in the case of calcium lead to kidney stones. Notably, the traditional recommendations of doctors to reduce protein and calcium intake are still persisting in John Doe's common knowledge - not just in the case of a kidney disease but generally! But these recommendations are virtually based on nothing but the (already since a long time ago available) analysis of calcium in kidney stones. Nowadays it is clear, that a calcium-poor diet increases markedly the risk of kidney stones. The reason is that already in our intestines calcium is continuously bound to oxalic acid, an organic acid from vegetables, which is a normal and harmless process. Thereby calcium and oxalic acid bind to each other as crystals, become unavailable for absorption into our blood, and are ultimately excreted from our body without any negative side-effects (except for the loss of calcium as a nutrient).
By means of a high dairy (and consequently calcium- and protein-rich) diet, calcium outcompetes oxalate and binds it already in the intestines, the formed crystals are excreted. In consequence less free oxalate but more unbound calcium is absorbed from the intestines into our blood. As a result, no more crystallization and formation of calcium-oxalate stones occurs within our system, i.e. in the kidneys, because the critical oxalic acid concentration for kidney stone formation is not reached anymore.
It is further true that dietary protein restriction in chronic renal disease does attenuate the kidney filtration rate, meaning less work load for the kidneys with less dietary protein - at least on the short term! Only the first 4 months of protein restriction (0.58 vs 1.3 g protein/kg body weight) showed a clear renal discharge (p=0.004) between the diets, but when comparing month 0 to 36 no difference between treatments was found! Notably, even with the diagnosis "chronic renal insufficiency" a daily protein intake of 0.8 g/kg body weight is recommended, which is about - surprise, surprise - as normal a protein recommendation as it could come from any dietary organization for healthy people. Translate it into foods, and you end up with a recommended daily intake of dairy products and 3-5 dishes of meat or fish per week.
Truly, for healthy athletes and also from the point of view of a hunter-gatherer diet, a daily protein intake of up to 2 g/kg body weight seems more appropriate. But this includes also high physical activity, plenty of fluid intake and a high consumption of vegetables and fruits as the main carbohydrate sources. Talking of modern protein supplements, which come as protein shakes, it should be kept in mind that even 3-4 such shakes deliver not more than between 60-100 g of protein in total - with a drink volume of about 700-1200 ml. Such a volume of highly satiating drinks does obviously self-limit its consumption. It furthermore constitutes just about 1.0-1.5 g protein/kg body weight. Furthermore, safety assessments regarding daily long-term protein intake consider intakes of up to 3-4 g/kg body weight as safe and beyond any health concern for healthy people. Summarized, a reasonably achievable high dietary protein intake is safe, and serious health concerns may safely be considered as modern fairy tales.