I think most people, by their very nature, are good people. And then there is the stiper...
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.