One definition of darkness is wickedness or evil.  In this case, turning darkness into the light means much more than just turning on a flashlight to remedy the absence of light (or some other means of illumination).

One approach to overcoming wickedness or evil is to expose it.  When all can clearly see the intent and impacts of dark behavior there is a chance to counter it.

Shining the Light

Injustice, flaunting societal norms, seeking not only to achieve pleasure for yourself but without regard to the impact on others is considered amoral.  Proactively acting in a way others may ultimately find unpleasant is just wicked.

Evil behavior is not always readily apparent, often not until it is too late.  Unscrupulous practices are often hidden from view (kept in the darkness) and the damage has long occurred by the time the evil is identified.

Fear

Fear can be a motivating factor for inaction.  We see and hear the evil but are too afraid to speak of it.  Shining a light, that exposes wickedness to scrutiny can sometimes backfire on us.

You can become a target of the evil-doer.   Their personal and earned power can make it difficult to challenge and although you feel the moral imperative, the negative consequences may be too great and you remain silent.

For the Greater Good

Tolerating evil practices may be okay for you personally.  Your awareness can enable you to dodge the bullet.  What about the potential suffering of others.

Consider the greater good.  Take action, join together to defeat the evil.  It is for everyone.