Darkness is not evil. Darkness is only what we cannot see. Some of what is in darkness is just there. Some of those who dwell in darkness are there because they do not wish to be seen. There can be many reasons to want to hide. Some of those who dwell in darkness are there because they cannot leave. Others stay because they will not leave those who cannot leave at the mercy of those who hunt in the dark.
It is dangerous in the dark. Even when there is nothing that wishes you harm, you may not see dangers to avoid them, or those who are dangerous may not see you to avoid you. Many predators can see well or otherwise find their way in the dark. They might take easy prey.
It is easy in the darkness to decide you must be either predator or prey. Even in the dark though, there is good and evil in all of us. The prey may grow powerful and become predators. Power does not make one a predator though. The greatest power is needed to protect. Keen sight is needed to see through the darkness. Fortitude is needed to bear the injuries meant for the weak. Greater strength is needed to restrain than to attack, because there is good in all, even the predators. Patience and will are needed to protect without oppressing.
Light is not good. Light just means something is illuminated to be seen. Just because it walks in the light does not mean it is not evil or dangerous, it just means it is either better at hiding its unsavoryness, or powerful enough not to need to hide. Light can lead to complacency, and too much light can blind. Evil and dangerous things can want the security of seeing around themselves just as much as the good and the weak.
It is dangerous in the light. It is easy to believe what you cannot see cannot be there. It is easy to lose fear and respect for the monsters when you see them in the light. Just because you see something does not make it not dangerous. Just because you see much does not mean you see all. Also, it is easy to forget that no matter how well lit it is where you stand, darkness is never far away.