It does seem wrong that we have to have specially reinforced ambulances, specially constructed wide beds,have to use equipment normally reserved for large animals for a small number of individuals who are so obese that normal equipment will not do. The temptation is to turn them away until they have lost enough weight to use existing equipment.
Start imposing arbitrary rules like that though, and you are moving very much into "nanny state" territory - if you impose rules for this type of patient, it would not be too much of a stretch to deny treatment based upon a patients smoking or drinking habits, for example.
At the moment, procedures and treatments are based upon clinical judgement. Generally I think that should remain the preferred option, apart from areas like transplant surgery, where organs are scarce, and the waiting list is much greater than the available organs.