I’ll let this Union soldier who met Robert E. Lee in the worst of circumstances tell his own story of how Lee lived out Luke 6:28  .  I think any further commentary from me might be considered to be vainly superfluous …

“I was at the battle of Gettysburg myself, and an incident occurred there which largely changed my views of the Southern people.  I had been a most bitter anti-South man, and fought and cursed the Confederates desperately.  I could see nothing good in any of them.  The last day of the fight I was badly wounded.  A ball shattered my left leg.  I lay on the ground not far from Cemetery Ridge, and as General Lee ordered his retreat he and his officers rode near me.  As he came along I recognized him, and though faint from exposure and loss of blood, I raised up my hands, looked  Lee in the face, and shouted as loud as I could, ‘Hurrah for the Union!’  The general heard me, looked, stopped his horse, dismounted, and came toward me.  I confess that I at first thought he meant to kill me.  But as he came up he looked down at me with such a sad expression upon his face that all fear left me, and I wondered what he was about.  He extended his hand to me, and grasping mine firmly and looking right into my eyes, said, ‘My son, I hope you will soon be well.'” 

“If I live a thousand years I shall never forget the expression on General Lee’s face.  There he was, defeated, retiring from a field that had cost him and his cause almost their last hope, and yet he stopped to say words like those to a wounded soldier of the opposition who had taunted him as he passed by!  As soon as the general had left me I cried myself to sleep there upon the bloody ground.”

(“Memoirs of Robert E. Lee”, by Col. A. L. Long, p. 302)