I was just on DeviantArt and I saw a thread bashing fat people. There was a link to the National Association to Advance Fat Acceptance website. Then came the hate. Personally I don't see why people care if others are fat. It's not any of their business and to hate someone because of it is just stupid. It's like smoking. It's unhealthy but there's no reason to hate someone because of it plus, there's no such thing as second hand obesity. Some people are genetically predisposed to have lower metabolisms or hormonal imbalances and such so it may not even be their fault. Sure, there are a lot of people who just lead an unhealthy life style but why discriminate against them like they're bad people because of it?
TL;DR= People hate fat people for no good reason.
I have not seen the thread, so I cannot speculate as to what counts as hatred or personal belief. However from a pre-medical and exercise science point of view, I can say that it is almost heartbreaking to see people that are highly overweight for a number of reasons.
As you stated, some people are predisposed to some hormonal imbalances. In this case, I would be heart broken because I find it painful to see an individual in poor health when it is not their own fault. I relate to patients who seem to have bad luck and share my sympathy with them as I know what they're going through because of weird and random health issues of my own.
Some people may also inherently possess lower metabolisms. This can be fixed with a number of medications. For those that do have the financial stability to afford these medications there are numerous steps that you can take to raise your metabolism. Your body is constantly trying to maintain conditions that are consistent with its environment (this is better known as homeostasis). When you're used to eating one massive meal a day, your metabolism hits a standstill. It is only working at it's peak at one period of this day and then shuts down. This can lead to copious amounts of unhealthy weight gain. One way to speed up your metabolism is to consume approximately 5 smaller meals a day at strategic intervals. By consuming healthy foods over the whole day, you're metabolism is constantly at work to break the nutrients down. Doing physical activity such as weight lifting and cardiovascular activity raises your heart rate, which will increase your metabolism and burn calories. In my opinion, the patients in this category have almost no excuse for their obesity.
I find myself to be highly disapointed in those that quite literally have no excuse to be overweight. My father for example was a lean and extremely fit 130lb young man when he graduated high school. Old age has a bit to do with it as his metabolism naturally slowed down, however due to lack of exercise and an extremely poor diet, he is now well over 200lbs.
I myself would never hate someone for being overweight. In fact, I would say in most cases, it is near impossible for a human being to hate another due to their body weight and appearance, with some few exceptions. But due to my interest in health, I cannot help but pass judgement on the people that are not proactive. Possibly the bashing you encountered in this thread was more of this nature and not of hatred. Or, possibly it was someone criticizing themselves for being overweight.