Eye for an eye was't obligatory revenge, eye for an eye was intentional and intelligent mercy. Back in the day the punishment often out weighted the crime, at the risk of overly simplifying it eye for an eye was much better than eye for a life.
In what ways can I be intentionally and intelligently merciful today? Maybe a better word for "merciful", in this context, is patient. How can I love those who put me down? Serve those who label me closed-minded? Minister to those who consider me stupid or weak?
First step is to be intentional. Ask the Lord to show us their beauty, and realize that they too were created for great and wonderful things. So we can see them for who they are, despite what they are doing and how they are acting. The next step is to be intelligent. We MUST ask the Lord to give us discernment on how to interact with them. I would argue that spiritual warfare is much more of an art than a science. Being sensitive to the Holy Spirit one step at a time will help us minister to each individual we encounter. It might be sitting down and talking with them about Christ, it might be sitting down and talking to them about Downton Abbey. Most of the time it's just being being a patient and humble person, who is willing to smile and wave on a regular basis.
Ask the Lord show you the beauty around you, and turn the grey into color.
Trust me, it makes this life much more fun. Not easier, just better.