Let's say you were a doctor. And you had a patient. And he had AIDS. And it was totally his own fault. You know that he contracted from unprotected sex or sharing needles. Would you still treat him? But, how could you help fight AIDS when he totally did it to himself?
What about a patient who has emphysema or lung cancer but smoked his entire life? How could you help him fight the emphysema or lung cancer when you know he totally did it to himself? Does he really deserve a doctor and medicine when he did it to himself?
What about a kid who comes into the emergency room? He was doing stunts with his motorcycle and pretty much nearly killed himself - now he needs emergency surgery in your E.R. Does he really deserve it? How can you, as a doctor, help him, when he was just so reckless himself?
Even worse, what if he killed someone else with his motorcycle stunts? How could you possibly help him?
Shouldn't you just sit back and let those patients die? Shouldn't that patient just take his death sentence like a man instead of trying to find a "loophole" like medicine? Shouldn't he just kill himself immediately to save everyone else the trouble? After all, it's his own fault, shouldn't he just accept responsibility?
It's not perfect, but after five years, it's the best response I have to "How can you represent someone when you know he's guilty?"