Man is born wicked. The Bible gives us the history of man's disobedience to God which caused his fall. The arrival of Jesus Christ provided man a path to salvation through faith in Him.
This is the most common mistake in world view. Is man basically good or bad? Those who believe man is basically good are usually the most shocked by the unprovoked evil of others.
If you watch the behavior of a baby growing as a child, you can see the inherent selfishness. The child must be taught good behavior.
Liberals. That's why they concentrate on environmental factors to try to correct the evils of society. They believe man is good and his circumstances (guns, poverty, etc.) make him bad. There is no solution there.
People are neither inherently good nor inherently bad. What they are is inherently self-interested. To the extent that people's perceived self-interest coincides with what is good, people are good. To the extent that people's self-interest coincides with what is bad, people are bad.
This is a key point which liberals completely fail to grasp.