It was about 10 years ago, when I was volunteering in my son's 6th grade classroom. It was Ramadan, and one of the girls in his class was wearing a headscarf. I overheard her telling the children about how she had to fast, that she would not be able to eat anything until sundown. Her classmates were asking her all about it. How could she go all day without eating? Why did she have to do that? It was wonderful, because the kids were so nonjudgmental, just genuinely interested and curious. And she responded to their questions with openness.
I believe children are very capable of empathy toward others because they are so used to so many things being new to them in this world. Every day, they learn something new... about life, about nature, about other people, about math, about so many things. That's the nature of being a child. Learning about other people, in an uncritical way, is a natural experience for children.
Even young children can learn to be empathetic. In fact, it is a critical human skill. Preschoolers first express their empathy for other children in the context of others getting hurt. Even toddlers will cry in sympathy when another toddler cries. And preschoolers will try to cheer their friends up, in their own way. This usually means doing a pratfall to make the other child laugh. Or it can mean just giving their friend a big hug. The child is not hurt himself, but he can understand the experience and take the other person's viewpoint.
If adults could be as open as children are to the differences as well as to the common humanity of all people, the world would be a lot better off.