I’m profoundly ignorant about medicine because I said a 52 year old diabetic should get the Covid vaccine?

Go **** yourself, tool.
You are proving, for the 1000th (?) time, that you revel in your ignorance. What is SIL's A1c? You don't know. What medication(s), if any, does SIL take for his Type 2? You don't know. What is SIL's blood pressure? You don't know. Does SIL have any family history of heart disease? You don't know. Does SIL have any indicators of heart disease? You don't know. What is SIL's current weight? You don't know. Does SIL have any signs of neuropathy? You don't know.
The only thing you claim to know is, "sTeeLeR In LeBaNoN Haz To TaKe ShOtZiNe!!"
Your ignorance is so profound that it should sit on top of a mountain, issuing words of stupidity to the dumb who make the arduous climb to receive your grotesquely moronic advice. "Oh Great Ignoramus, I am looking for a way to keep brisket moist when I smoke it. What do I do?" Floggy: "gEt ThE ShOtZiNe!"
*sigh* You are an idiot. But try to learn something about diabetes. Type 1 diabetics fail to produce insulin. Type 2 diabetics produce insulin but their metabolism can no longer process the insulin to convert carbohydrates into useable energy. The result is that the excess food energy (sugar) flows into the blood stream as a waste problem to be eliminated. The process causes the thirst and urination which is a sign of diabetes as the body is trying to eliminate the excess sugar from the blood, a process the body cannot win without medical help.
The excess sugar flooding the blood stream causes the hemoglobin to bind with glucose, which unfortunately increases blood viscosity. The increased blood viscosity reduces the amount of blood that can flow to very small blood vessels in every organ in the body. That reduced blood flow can cause liver and kidney damage, vision problems, neuropathy, and for Type 1 diabetics a really nasty, painful death in a matter of days. The key here is to control blood sugar. That is it. Injected insulin or oral medications, controlled diet, and exercise are the ways to minimize and essentially negate the adverse effects of diabetes.
For SIL, his weight loss and medication likely reduced his A1c to something around 5.8, a level associated with "pre-diabetes." I say "likely" because I don't actually know and unlike you, would not pre-suppose anything about SIL's medical condition. If SIL indeed has his A1c at 5.8, he would basically have no more "risks" from Covid than most non-diabetics. See the risk of Covid to diabetics arises from those who do not control the diabetes, since the high A1c results in hemoglobin binding with sugar, lowering blood flow to the small blood vessels in the lungs, and essentially "feeding" the disease with the excess blood sugars. For a person with an A1c of 5.8 or below, that risk is essentially non-existent.
You're welcome, you ignorant slut.