This known as the problem of evil.

Buddhism would say bad behavior is due to ignorance (that begs the question, and hence is an unacceptable answer).

The only religion with an answer is Christianity (Judaism has no bona fide answer), so do some reading at the library.

A good place to start is C.S. Lewis' Problem of Evil.

As currently defined, the atheist does not believe God exists, and the agnostic does not know if God exists. (Thus the agnostic is actually a timid atheist.)

When the words "I ought to ..." are uttered, then the moral imperative is invoked.

The free choice to make this utterance proves the speaker is a moral person, has conscience, and hence knows the difference between right and wrong.

When the atheist and agnostic say "I ought to", they contradict themselves as claiming to be such.

The Roman Catholic Spanish philosopher named Uanmuno y Jugo said:

"Those who deny God deny Him because of their despair in not finding Him."