Human beings are natural liars. The author you've linked to and the people she quotes are all pushing a thesis not because they've considered all sides of the issue, but because it strokes their ego to be contrarian.
Obesity is not a risk factor for coronary artery disease. No one says it is. Hypertension, diabetes, cigarettes, high LDL and family history are risk factors for atherosclerosis in coronary arteries, for stroke and anywhere else in the body. I spent my career reading articles documenting that. It's not some fantasy.
Most people who are obese do not have hypertension and diabetes, yet. The rate of diabetes keeps going up. Is the combination of obesity and lack of exercise making the risk for diabetes from obesity worse? It's hard to say. But it's not hard to say that obesity increases the risk for hypertension and diabetes. I've seen it in my own body, leading me to take antihypertensives in my forties and to suddenly have a blood sugar over 500 in my fifties. Losing 60 pounds fixed that. It made my fatty liver go away. It had all sorts of benefits.
Now this article makes a big deal that the death rate of those with a BMI less than 20 is high. Do you know what someone with a BMI in the teens looks like? I'm 6'3". For my BMI to be under 20, I'd have to weigh less than 160. I'd look like a survivor of a prisoner of war camp. The tables of ideal weight don't go that low. They're based on many studies of mortality and are reliable.
PT Barnum was right. There's a sucker born every minute. Anyone who wants to embrace an article like this one to say there's nothing wrong with being overweight can do so. Maybe time will prove them wrong as my complications of obesity taught me. Maybe they'll die from something else before they get any complications of obesity. It sounds like natural selection to me.