This is about evolution. Those at the top of the food chain have always eaten everything lower down.
Humans can reason and think about their actions rather than simply rely on instincts.
We can analyze our behavior and make choices based on thought.
We can therefore, empathize with other life forms. We can put ourselves in their place and think how we would feel.
Of course, some use the capacity to think more than others...as is clearly illustrated by the varied comments in this thread.
