If you reduce them to singular acts, that is feeding a hungry person and smoking in a restaurant, arguably one is actively doing specific harm (carcinogens) while in the other case it's hard to deduce a specific harm from the act. In the case of feeding a person, I have heard arguments about _general_, long-term, associated harm to property values and averaged crime rates. Conservatively, when looking at a principle cause, there isn't a good reason to ban feeding the homeless.