I would not write it this way today.
That is one of John Piper’s reflections almost forty years later on his 1974 dissertation, Love Your Enemies, just republished by Crossway. It has to do with how he approached the topic in the Bible.
In the "thicket" of world-class scholarship, Piper employed a "history-of-traditions" method to his study which requires a great deal of research "behind" the biblical text. The point is to discover different sources outside the New Testament that are responsible for what's there. And the reason he'd write it differently now is because there's another approach to biblical studies he thinks has a greater payoff. He writes in the new preface of Love Your Enemies,
... since you only have one life to live, the payoff historically, theologically, spiritually, and practically will be far greater if you focus your prayerful mental energies like a laser on the text and the biblical context itself. Most of what I saw of value in my research I saw by looking at the texts themselves, not by being aware of sources. (viii)
He also adds,
If you want to see how I would write a book today on Jesus' command to love our enemies, read What Jesus Demands from the World (Crossway, 2006, especially chapters 28–31). That book reflects my seasoned judgment about how to do Gospel studies for the greatest payoff. (ix)
In that book, Piper's conviction on how to approach the Bible can be clearly seen. In fact, in a chapter entitled "A Word to Biblical Scholars," after reflecting on his days in Germany and positive influence of Adolf Schlatter, he writes,
The conviction was growing in me that life is too short and the church is too precious for a minister of the Word to spend his life trying to recreate a conjectured Jesus. There was work to be done — very hard work — to see what is really there in the God-given portrayal of Jesus in the New Testament Gospels. (32)
In sum, because we only have one life, and that life is too short, let’s give ourselves to the biblical text.
Related posts to the republication of Love Your Enemies: