BMI works just fine for someone weighing so much that they need to go and find a special scale to measure them. Already before you're obese it'll be difficult

BMI works just fine for someone weighing so much that they need to go and find a special scale to measure them. Already before you're obese it'll be difficult to give someone CPR. If someone is obese that's dangerous already. It's completely normal and logical response to tell them to lose weight.