Ask HN: How do you deal with abject poverty around you?

I'd like to get thoughts on a specific incident that happened to be last night. I was in Manhattan (at a McDonalds of all places). A teenager came in (he had a slice of $1 pizza) ... he sat around for a bit and came to me to ask me for the food I was eating. I said no. The reason I said no was because I wanted to discourage him from begging for food. He persisted for a quite a bit. I engaged in a bit of conversation with him to understand why he was begging, why didn't he get a job, etc. This kid seemed to be on another planet ... "you have money. you can just buy more food ... I want your food ... give it to me". It was a bit surreal. I threatened to call the manager, but that didn't make a difference. After a while, I just gave up in disgust and gave him my food. Just to be clear ... giving him food or charity was not the issue here (at least from my perspective).

The whole episode has got me confused from an ethics standpoint. I feel I am a lucky person and probably should give more charity. At the same time, I don't want to encourage such unacceptable behavior .. especially in a teenager who has his whole life in front of him. What was the right thing to do in such a situation?

In retrospect, I should have asked him for something in exchange for the food. Maybe do a quick errand for me. E.g. buy me gum or give me a napkin. Try to impress on him that he had something of value to give. Maybe I should not think so much and ignore aggressive begging. I am very confused and in some pain. Are there ethical principles to guide me here?