First of all, it is the consensus of Muslims, Hindus and even humanists, deists and most atheists that Jesus was one of the greatest people to have ever lived. Again, even to the non-Christian, Jesus would be a consensus choice for the most ethical, sacrificial, loving, “good” person who have ever lived, alongside with Mother Theresa, Mohatma Gandhi, Nelson Mandela, Martin Luther King, Albert Schweitzer, Socrates and a few others. The charge that he was an immoral person does not hold water to any reasonable person, and the fact that an atheist would claim Jesus was an immoral person shows just how desperate that person is.
But, let me get to Matthew 5:39. In this passage, and actually from verse 38-42, Jesus is teaching non-resistance to those who hate us and who treat us unjustly. If we are treated unjustly, we ought to “present the other cheek.” If we are asked to give our shirt, we should offer our cloak as well, and if we are asked, unjustly, to carry a load for a mile, we ought to offer to carry it an additional mile. Right after this passage, Jesus also challenges his followers to love their enemies. By what conceivable measure is this immoral? This is one of the most challenging principles ever offered to human beings. If everyone lived this way, the world would be a utopia. Violence, poverty, racism and greed would disappear. Immoral? Really? This is absurd.
By the way, this passage was the subject of the sermon that I just preached today. You can go to the web site and download the notes, the power point and the audio if you like. Far from being immoral, I would argue that Jesus was the most “moral” person who ever lived, and challenge anyone to come up with a close candidate for second in that position. You ought to completely ignore this ridiculous criticism.