In Star Trek Into Darkness, Spock claims he can choose whether or not to feel an emotion. Can humans chose how to feel or is this simply a Vulcan thing? The answer is that people can often act in a Vulcan manner and choose their feelings.
The human brain is hard-wired for empathy; in situations like this, we understand why. Helping those who suffer diminishes both their pain, and ours, preserving our fellow humans, ourselves and our species.