People do die of starvation on the streets, although it's not as common as dying of exposure, violence or drug/alcohol overdoses. And as to the smoking, you might want to read this link about how psychiatric illness and smoking are like peanut butter and jelly. Given that psychiatric illness and homelessness are also tightly correlated, maybe that might help you understand what's going on and be less judgey about it.
I'm actually going to congratulate you on being honest with yourself and willing to openly talk about this bias with your peers. Please keep doing this. Here's what you do about it: Don't work with the homeless. Don't do volunteer work for them, and once you're a doc, choose a practice where you can avoid working with them. The most compassionate thing you can do for the homeless is to stay away from them. But if you do find yourself working with someone who happens to be homeless, try treating them the way you would want you or a family member to be treated in the same situation - golden rule and whatnot. As someone who plans to primarily work with this population, I would appreciate not having to also try to shield this population of human beings from people like you. Kthx!
