While it's a nice mantra to state that all men are created equal, and that we are all blank slates, this is patently untrue. We are all born with genetic predispositions for various things. Some of us will be a little taller, shorter, faster, slower, smarter, athletic, and so on. This includes a wide array of harder to measure abilities such as empathy. However, just because we are all born with various degrees of empathy, very few people are born with out that ability. Some are, but they are the exception not the rule. With empathy comes the basis of inherent morals. We as social creatures can empathize, and thus relate to one another on an emotional and physical level.
http://chronicle.uchicago.edu/080814/empathy.shtml
Again, the brain is hardwired for certain chemical responses. When we see pain in others for the first time there is a measurable chemical response in our brains. It is an empathic response to the plight of others.
It takes a LEARNED behavior to overcome our natural response to these situations.