To the contrary, ‘if your enemy is hungry, feed him; if he is thirsty, give him something to drink; for by so doing you will heap burning coals on his head.’ Do not be overcome by evil, but overcome evil with good.” (Romans 12:20-21)
What Paul says here applies to our actions and attitudes to both our brethren and non-believers .We are to bless those who do not wish us well. We should not seek to afflict others with pain, be embittered at their success or rejoice in their misfortune. We should weep with them and rejoice with them. We should try to live in harmony with all people, as far as it is possible. 

In this time of social unrest, people want to take justice into their own hands and see that the offender suffers what they deem is sufficient punishment. In this way they usurp the place of God. But is this what God wants? No. We must trust that He will exercise justice as He sees fit. And that galls us. That angers us, because we think we ought to have the right to take our vengeance, to exact our pound of flesh.

Paul instructs us to live in harmony with all men, as far as our actions and attitudes are concerned. We should never compromise with evil or accept the false as true, but we should never respond to the sins and abuse of others in kind. It does not matter how others act; we have no excuse to do evil to anyone. We are not called exact vengeance. There are means we can use to see that justice is done through the government and legal system. But, we are not to sue for vengeance, or to exact harsh recompense over and above what is fair.

We are instead to always be doing good for others, not merely refraining from evil, but actually doing good. By doing so, we heap burning coals on their heads, not to burn them with punishment but to burn them with shame so that they may see their sins and repent. When they see how good we are to them despite how they treat us, when we return good for evil, perhaps they will feel shame. Maybe they will stop their behavior, and we have won them over. Maybe they won’t. Then, it is up to the Lord to judge, to exact His wrath.

Jesus is the example for us to follow. If we claim that we belong to Him, if we say we want to live as He did, why do we shame Him by our lack of love? Why do we disobey Him by showing little respect for both our brethren and for those in the world? If we say we are His, then we must act as He did. We must do what Jesus did, forgive, love, do good, and lay down our lives for others.