See my links in the thread below. Particularly the one by Dr Paul Mason. Observational research with lots of confounding factors.

Big food does not make much money on meat. Lots more profitable to take cheap commodity ingredients and make nutritionally inferior plant based products in a box or with a bar code. So they grasp on whatever research they can muster to promote eating more of the stuff they make and discourage the use of nutritionally dense but minimally processed meat.

This is so informative, I will link it again here.

https://www.youtube.com/watch?v=0b8Osg5MbfE

If you want to learn about red meat and diabetes, look up Dr Ben Bikman (PHD research scientist, not a medical doctor). His specialty is insulin and its effects. He has good presentations on how protein, fat and carbohydrates (the three macro food groups) effect blood sugar, insulin and diabetes. Short answer. Carbohydrates do. Meat protein has minimal effect (although somewhat additive if consumed along with carbohydrates which serve as the insulin trigger). Animal fat almost no effect.