Your are a heartless d-bag if your like, "haha, starving kids, haha, third world countries. etc. etc."
But if your like. "Sucks for them, but what am I going to do?" And then you ignore it.
I don't 'care' I think it sucks for them, I am glad some organizations help the starving kids, but other than that I don't care. If you can't do anything and put it out of mind, then no your not heartless. If you could do something, but just didn't then you probably are a d-bag.
Someone told my uncle once, when he didn't finish a meal and threw it away. "You know there are starving kids in africa" To which he replied. "What the fuck do you want me to do? Mail them my leftovers?"