The things people feel they have permission to say never ceases to amaze me... Fat phobia is deeply ingrained in our society. It is a sad thing because being fat is still seen as lazy or a morality issue instead of the medical issue it truly is. Just because we need support and sometimes surgery to deal with the weight doesn't mean it isn't a medical issue. People who are thin and have been thin all their lives can be really narrow minded about weight. They think they are incredibly self controlled and virtuous to maintain their weight, instead of realizing that most times it is luck of the draw...
No one in my immediate family is as heavy as I am by any means, and in fact my sister barely touches 100 lbs. She's healthy, she's just naturally tiny. She's always been angry at the comments I get because she knows that she eats more food and more crap than I do, especially when we were younger, and yet she struggles to maintain weight and I can't keep it off. I adore her because she celebrates every win I have regarding my weight because she understands how hard it is. People can be biting to naturally tiny people too... My brother on the other hand is supportive but is very fat phobic. He gains 15 lbs and calls himself a fat ass and obsessively works out at the gym until he can get it off. He doesn't understand the struggle at all.
I've been very open with everyone I know about the surgery because that's just how I live my life. Most are wildly supportive because they know how hard it has been for me... I'm sure a few silently judge me but they can keep their thoughts to themselves. I don't make space for their bullshit. The best way to deal with that crap is exactly what you did, to tell them to stop and show visible disgust. I react that way to other discrimination too, it is very useful for shutting down a conversation! LOL