Most if not all of the questions in your last post are answered in the medical fitness for diving guidelines, the link is
HERE
These sections specifically:
2) Hyperventilation and panic stress reactions are more likely to occur in the physically unfit.
3) Physical fitness reduces the risk of heart attack, which is a major cause of diving fatality.
Our debate has come full circle and there's really nothing more than can be said at this point. If you can't grasp the simple concept that a fit diver is less likely to succumb to panic and suffer an injury such as an embolism due to an uncontrolled ascent while holding their breath; and an obese out of shape diver is more likely to suffer a heart attack while diving than one who is in good physical shape; then there's nothing more that myself or anyone else can say that's going to get you to see it any differently.
I agree with most of what you say, but, speaking as a person with a BMI in the obese range...
Being overweight (or large) does not present as many disadvantages underwater as on land. Think of the marine mammals.. Excellent divers, lots of muscle mass, layers of fat and they are still move through the water pretty well.
A diver who works out doing weight training and cardio exercise can be in reasonably good shape and be quite athletic, even though they are carrying around an extra 30 lbs. Not that it is healthy for them, but you can't really argue against the fact that the bouyancy provided by the water can mitigate the extra work associated with dragging this extra weight around.
In addition, in most dive conditions, having an extra layer of blubber provides significant thermal protection and this might be beneficial in a dive accident where the diver would have to spend extended periods in cold water. In addition the round guy might be able to wear less wetsuit thickness and this is certainly an advantage when you consider the undesirable effects of wetsuit compression.
Quite often heavier people who are active, tend to attain more muscle mass than some thinner people. Having a reserve of muscular strength can be beneficial when handling heavy scuba gear on a boat.
The additional hydrodynamic drag asscoiated with a bigger gut (or fat ass) is probably insignificant compared to the drag from the scuba unit itself and often, heavy people have very strong legs and can kick better than skinny, little people, especially if they engage in athletic training.
Americans are way too fat and out of shape, but it is quite possible to be a pretty good diver and still have weight to loose. I suspect that the biggest drawback (from a diving perspective) of the extra fat might be associated with inert gas absorption and diffusion, but even that might be mitigated by having a high level of cadio fitness.