Star Wars: I Feel a Conflict 

Scenes from Star Wars episode VI Return of the Jedi: Luke Skywalker tries to bring his father Anakin/Darth Vader back from the dark side.
When the 'dark side' of human nature is not kept in check it can unleash a savage deadlier than any other animal, capable of the most heinous acts of depravity and destruction. Contemplate that and you will understand how and why religion came into existence and why man has always aspired to be better than what he is.
Every system of belief is, at its core, about the timeless epic struggle within the heart of man to purge the savage within himself. Human history and folklore is steeped in the mythology of good and evil, saint and sinner, god and the devil. Such legends were spawned out of our own desire to defeat the savage by the simple and noble virtue of being good and honorable. It's a mythology that is retold a million different ways in our fairytales, books, films and music - the story of good triumphing over evil; struggle overcoming adversity; man overcoming nature (within himself and his environment).
There's no right or wrong, good or bad about anything however. Moral issues originate through culture, informed by nature. Nature informs our emotional and intellectual disposition but does not deify us with moral virtues. We have to earn our moral virtue by maintaining rhythmic synchronicity with natures eternal heartbeat. Morality is something we construct, together, using our shared emotional and intellectual experience to inform what we all naturally have in common. Whether we are consciously aware of it or not, our emotions are pushing us always to resolve our loneliness through kinship and cooperation with others.
The culture we live in suppresses our true savage nature and substitutes it for conduct and values that make us "civilised" using coercion, force and oppression. Every culture has its own morality and definition of what "civilised" is, but it's mostly an artificial construct. Culture and indoctrination can make man a terror or a saint in the name of "good" and "love" depending on his ideological beliefs. Stalin, Hitler and Genghis Khan believed they were doing good.
Man is an emotional being, but is not a peaceful and loving creature by nature. The conditions which temper his emotions depend greatly on circumstance, which can elicit either violent or peaceful outcomes. He will take up arms in defense against his fellow man unless he finds reason to cooperate for the mutually beneficial advantage. And when mutually beneficial concerns involve the oppression and killing of others in pursuit of a collectively shared belief, then what he deems to be "good" becomes oppression and death for others. Man is certainly capable of love and kindness, but only when this is fostered through appropriate nurturing from infancy to assuage and tame the beast within.
No civilisation is justified if human beings are not informed by nature as the standard bearer upon which we legitimise a common basis for constructing the principles of right and wrong, good and bad. Our moral sense of purpose must therefore rely on our ability to recognise and identify suffering, and work towards reducing it and eliminating it in our lives and in the wider world, as well as in our political and social institutions and cultural arrangements.
You cannot just be a good man. You can only become a good man. The former is a contrived act; the latter is the real you once you have earned it through self-discipline, and by not succumbing to innate savage impulses from within. It all depends upon how we respond to the evil we experience in our lives and whether we turn that experience into a force for good or ill.
Do we remain savages - embracing selfishness, greed, corruption and oppression - or do we endeavour to purge ourselves of these undesireable qualities and replace them with trusting, selfless values of caring, sharing and kinship, in mutual cooperation with others? The latter is essential for developing a civilised society; the former is not. One serves to alleviate suffering and appraise liberty and freedom; the other exacerbates cruelty, oppression, death and destruction.
Hatred, villainy and savagery is easy, but it will destroy you in the end. The real test of your humanity is within your courage and capacity to purge the savage within, or be easily seduced by it. Every single human being endures this epic struggle of duality until they are finally resolved in mind and body to peace, or nirvana - call it what you will.