Well, I am one of those dreadful overweight people, but you won't catch me in the swimming baths, precisely because of people like you.
What you wouldn't know from looking at me is that less than a year ago I was two stone lighter, very fit and did circuit training 6 days a week. Since then I have had an injury which immobilised me for several months and a sudden decline in a health problem which means I am unable to exercise.
Swimming, or at least movement in water would be a good way for me to restart exercising, but I am so distressed by my weight-gain and unhappy with the way I look that I simply don't have the confidence to put a swimsuit on.
Fwiw, I am vegetarian, don't eat processed food and have 3 dcs and a dh who are all built like whippets!
Perhaps you didn't mean your OP to sound like you judge every single overweight person you see, but it doesn't help people like me to think that others are looking them up and down and thinking about how fat I am.
If you have a point to make about your concern for the rise on obesity, there are lots of other ways you could have raised the subject for debate without targetting overweight people who are trying to do the right thing and get some exercise.