It's because anesthesia becomes a million times more difficult with obeasts. Granted, I only studied veterinary anesthesia, but I imagine things are quite similar. If you're obese, you could have any number of comorbid diseases that go along with it. High blood pressure, for example, could cause the patient to stroke out. Anesthesia could induce a cardiac episode in a patient that already has cardiovascular issues. Respiration could stop during anesthesia. And in addition to all these problems, the anesthetist can potentially have more trouble keeping the patient at a good plain of anesthesia - too much anesthesia and you'll die, too little and you could wake up during the procedure. In animals we calculate drugs based on weight and species, but I'm not sure how they do it in people. I imagine it's similar. When we had obese patients (yes, cats and dogs can be obese too) we would have to calculate based on "ideal weight". So for example, we'd have to figure out what the average weight for a chihuahua would be, instead of calculating for the dog's actual weight of 25 pounds. Because it's an educated guess at best, the patient might not be at the correct depth of anesthesia, or they might not have received the correct dose of narcotic pain medication to ensure that they are comfortable upon waking up. But of course, obeasts overlook all these factors. They think everything that is in opposition to what they want is discriminatory. They don't bother to ask "why", they just want what they want when they want it.