Capital Offense in The Bible: Hitting a Parent (Exodus 21:15)

Whoever hits his father or his mother is to be put to death. -Exodus 21:15 GNB

Another punishment that doesn't fit the crime. Which is worse: hitting a parent or murder? The Bible appears to hand out death sentences left and right, but doesn't see how killing another human  is wrong. It views all bad actions as evil ones, and all evil must be eliminated. The writers view unjustifiable killing as righteous.