Earlier quoted context omitted.
I don't really get your second paragraph. If you can afford to help strangers, then you can afford to help your friends. What point are you trying to make? I'm not sure. And why do you help your family and friends? Why not focus on yourself only? My point is, why did you draw the line exactly at friends and family? You don't owe anything to the rest of society, nor the rest of society owe anything to you? Why do you…
Why draw the line at family and friends? It's a natural place to draw the line. I think if you study psychology and the evolution of the human mind that's pretty obvious. Additionally if you want to reason in a framework of debts, then you probably owe the most to your friends and family. You owe your entire existence directly to your parents -- it's hard to top that! Might as well stop there and just accept you have…
I think if you study those things, you'll realize that it's not at all obvious. Clearly there's a difference between your blood relatives and the rest of humanity, but we collaborate and dependent on non-related strangers far more than any other species, and we have morals that support that kind of behavior. Why, do you think, we accuse people of nepotism, when they favor family in some scenarios (particularly in business and politics)?
I think the slogan "charity begins at home" is not appropriate to excuse one's ignorance of others' plight, and the fact that we have this debate is a good proof that human ethics are, in fact, more sophisticated.