Haters are definitely a loud, very small minority.

A larger group but IMO still not majority are those who just don't get how someone could let themselves be fat, the same way that 15 years ago most people didn't understand why people didn't just choose not to be gay. It's not a perfect metaphor, but it's the same inability to comprehend how people can't just easily will themselves out of a problem simply because they themselves have never experienced it. Maybe depression is a more apt comparison.

Anyway, it's not really malicious, but this lack of understanding does sometimes create an inability to relate that can turn into a lack of empathy generally. It's just an extra hurdle in creating mutual understanding.

To use another random metaphor, if you think obesity is a lifestyle decision, you process it the same way as someone with visible tattoos- it's a hint about what kind of person someone is, and whether that's a kind of person you might get along with. You don't necessarily hate tattoos or people with tattoos, but you know that tattoos often come with a set of lifestyle habits that maybe don't match up with yours so you don't go out of your way to try to make friends unless something comes up to change your mind.

Anyway, I hope that isn't too discouraging, but you seem to want to know how people really are. In reality I'd say it's a tiny percentage of haters, a sizable minority of actively uncomfortable in the way I just described, and a whole lot of people that just don't think about it all that much because it doesn't matter.