The cost of evil.

"... but I will recompense their wicked doing upon their own heads." 

-Ezekiel 9:10

Yes, revenge and anger will flow through your mind when you come across vindictive, hurtful, hateful, lewd, wicked, or spiteful people.  However, your line of duty is to immediately pass that person, or those people, over to God; pray for them, forgive them and walk away!  

Remember, you have much better things to do and live for anyway!

A fools folly

"Answer not a fool according to his folly, lest you also be like him..." Proverbs 26:4

and remember:

"As a dog returns to his vomit, so a fool returns to his folly." Proverbs 26:11

Therefore,

Do not worry about prideful, spiteful wrong-doers, nor lose heart in doing good, staying calm, and taking the high road, for in due time and at the appointed season you shall reap His rewards, while the prideful, spiteful wrong-doer buries himself in a grave he's pre-dug for himself. (partially adapted from Galatians 6:9)