I get your point, but there are some people who have valid cause for their size. Pituitary tumor, for example. Without the job and the insurance, correction becomes financially impossible. I know a lady like this who is a nurse. In fact, nurses are sometimes more heavy than non-health professionals. That's kinda scary. Has to be partly due to the high stress. IMHO.
It's true that there are plenty of people out there that are unhealthy through no fault of their own, but that doesn't mean employers have any responsibility to subsidize them. In fact they have a responsibility to both their customers and their shareholders to do otherwise. The one exception would be if the conditions arose during employment and the employer was committed to provide for the employee per the terms of employment.
It's may sound heartless, but companies aren't in business to be charity cases and when we force them to be, they become less competitive and we all suffer because of it.