Mainstream medicine focuses mostly only on blood sugar control. And high blood sugar level is definitely a problem so that part is correct. That part is proven.

But another line of thinking is that high insulin levels in itself is also damaging. For everything from diabetes complications to other ailments like cancer and other non infectious diseases. This is mostly not acknowledged by mainstream medicine but is gaining traction from a greater number of doctors. Particularly the ones through their own practices have found benefit to maintain low levels of insulin by restricting carbohydrates to control blood sugar instead of using insulin or insulin increasing drugs most of which raise insulin levels to control blood sugar.

If this is theory is correct, then giving insulin to control blood sugar is adding to a problem of type II diabetics that already have insulin levels over the top. Kind of like giving a drink of alcohol to an alcoholic to lessen his alcoholic addiction symptoms. 

There is some research that supports this hypothesis. I can not quote the study but I have listened to several doctors that quote its results. It is a fairly old study and a very well run with high numbers of participants. A controlled study. One group ate normally and another group had their blood sugar controlled very tightly with insulin resulting in much better blood sugar control. Followed up for a number of years later. Yet the results were not as expected because after years of follow up the survival rate was no better in the group with well controlled blood sugar. That is not to say there were not health benefits to controlling the blood sugar. There definitely are. But the unanswered question not addressed is why the people were not living longer. Suggesting, but not proving, that the high insulin levels used to control the blood sugar levels had some unintended negative health effects.

And this is what a small subset of the doctors have came to believe. That excessive insulin levels are also harmful to the health. Not only high blood sugar that the current main stream medical industry treats with medicine and insulin, but also high levels of insulin that is a characteristic of type II diabetes and is made worse by treating with insulin. This is what I believe to be true based on what I think I have learned and it also jives with my own personal experience. It is why I control my diabetes type II with diet rather than medication and insulin. I took insulin shots for 25-30 years and diabetic medicine for even longer (started out on pills only, later as my disease progressed went to insulin shots). I have not taken insulin shots nor diabetic medicine for the last 7 years.

But I am often wrong, so don't anyone believe me. Do your own research and decide for yourself.