Prevail evil by knowing evil.

We fear what we don't know and understand.

Racism, abuse both verbal and physical. It goes on.

These things exist in the world, but why? Instead of reacting to their negative action with our own lets understand why they do what they do. 

A man wont hate another man purely because of his skin and looks, it is because he is different and he doesn't fully understand him (culture, language, looks, etc). And when they can't fully understand the other person they react out of violence and hate to stay protected. A defence mechanism.  The abuser doesn't really know why they're acting out in such a way, they just feel that reaction inside and have to let it out.

So, evil and negative deeds are prevailed once understood, no need to scoop to their level and play their game because you now understand something about themselves they don't.