I wonder if the shape of hunters has more to do with the average American waist line, than to say hunters are in bad shape. The other sports you mention discriminate on the basis that they require great physical shape in order to participate. The great thing about the hunting tradition in America is that it welcomes all shape, sizes, and ages, and discriminates against none.
To think that only skinny people should have access to our public grounds is not only a detriment to the sport, but is a one of many dangerous attitudes that could lead to the ending of our sport. If we as hunters stand divided, we don't have a chance against the anti hunting crowd, so we must be carefull when we pass judgment amongst ourselves. I can see your point of using an atv to go only a few hundred yards, but in our areas it is more like 10 to 20 miles, and I don't care how great of shape you are in, you are not going to cruse that off before daylight and then pack your game out on your back that night. I think a balance needs to be struck, and to limit access only to those who can afford horses, or are in iron man shape would cut the # of hunters by at least 3/4, which would lead to an overall ban on hunting.
I for one enjoy hunting on foot as stated before, but an atv is a tool that has its place, and just like any other tool it can be abused, but to make a sweeping judgment that atvs are all bad sounds allot like the anti-gun crowd stating all guns are bad, or rifle hunters saying that all skinny bow hunters are all self rightous snobs.