What happened with diabetics, I think, is they got the cart mixed up with the horse.
Since diabetics are at a high risk for heart disease, once low fat became the paradigm for avoiding heart disease, diabetics got told low fat. And we all know what that leads to.
I have heard from many open minded health care practitioners that low carb used to be the way to go for diabetics. And it still makes a great deal of sense to me.