What a wonderfully interesting thread on weight and responsibility in diving.
On the questions of the OP: I agree with the majority on here. Your freedom stops when you injure me. The fact that we have laws that cause injury to others for what should be "Darwin awards" is a problem in the legal system, not in personal freedoms. Don't break something to compensate for something else that is already broken. Others have said it better in previous posts.
On the issue of weight, I personally have never had a problem. I have watched a family member struggle with it and as such I am aware that telling someone to eat less and exercise, while true in the majority of situations, is not received well by the individual at which the advice is directed. They may work out, but that will trigger more eating. It is very difficult to work out, feel hungry, and then grab a granola bar for lunch.
After five years of frustration, what finally did work was an app on the family member's iPhone that tracked caloric intake. She was very surprised to see how quickly the calories added up, and just how little an hour on the treadmill would burn. After that, it was her personal battle to win or lose. Thankfully she has won that battle and is now healthy and fit. Bottom line, nobody wants to feel like a failure. Some have to battle harder than others to drop the weight and that can be frustrating. The solution may be non-complex, but the discomfort of eating less, working out more, and picking healthy foods is not easy.
Also, my family could make the case that I am "genetically predisposed" to being over weight as both my parents were fat and my father still is very overweight. At a young age I realized that I didn't have the high metabolism of some and adjusted my eating accordingly. Limited breakfast, snack at lunch, and a good early dinner get it done for me. Would I like to eat more? Yes. Can I eat more and stay fit? No. Now, I'm going diving...seriously.