It would be if this was actually happening, which is never. Maybe there's like a handful of shitheads out there doing it, but this isn't a wide-spread problem.
http://onlinelibrary.wiley.com/doi/10.1111/obr.12266/full
"Finally, physicians may over-attribute symptoms and problems to obesity, and fail to refer the patient for diagnostic testing or to consider treatment options beyond advising the patient to lose weight. In one study involving medical students, virtual patients with shortness of breath were more likely to receive lifestyle change recommendations if they were obese (54% vs. 13%), and more likely to receive medication to manage symptoms if they were normal weight (23% vs. 5%)."
> Comparisons of recommendation categories for shortness of breath by condition revealed that students were more likely to recommend lifestyle changes when the patient was obese than when she was not obese, χ2 (1, N =76) =14.6, p<.0001. They were less likely to recommend symptom management (i.e., bronchodilator prescription) for shortness of breath when the patient was obese, χ2 (1, N =76) =4.8, p<.05. There was, however, no significant difference in recommendation rates for diagnostic tests.
The article links to research showing that it is a wide-spread problem. There may be valid criticism of that research, but your flat unsupported denial is not that criticism.
It's not simply based on BMI. It's based a lot of things, but at some point the BMI will be bad enough that the other things become irrelevant.
>asking a 500lbs person to lose 200+lbs before you're willing to treat their disease with actual evidence-based medicine—looking at symptoms, pathology, etc—is tantamount to outright denial of care.
It would be if that actually happened in any systemic manner. And even in the cases where it does happen, it has less to do with whether the doctor is willing and more to do with whether the doctor is able to diagnose.
> But just saying "we have a BMI cutoff" is pretty much discrimination masquerading as medicine.
It's discrimination in the same way that saying people under a certain height can't ride rollercoasters. There isn't some conspiracy amongst theme parks to alienate short people. It's dangerous, and it's nothing to do with prejudice against short people.
And in reality, it's not "we have a BMI cutoff" as the only criteria. It's "we have an extensive and exhaustive list of things we look for before we recommend surgery to patients, since surgery is a dangerous and often life threatening procedure. One of those criteria is a BMI that doesn't cause undue risk to the life of the patient".