They are not giving back anything except condemnation, often depicting sins common to the human race around the world as peculiar evils of "our society."
A classic example is slavery, which is repeatedly drummed into our heads -- in the schools and in the media -- as something unique done by white people to black people in the United States.
The tragic fact is that, for thousands of years of recorded history, people of every race and color have been both slaves and enslavers.
The Europeans enslaved on the Barbary Coast of North Africa alone were far more numerous than all the Africans brought to the United States and to the 13 colonies from which it was formed.
What was unique about Western civilization was that it was the first civilization to turn against slavery, and that it stamped out slavery not only in its own societies but in other societies around the world during the era of Western imperialism.
That process took well over a century, because non-Western societies resisted. White people, as well as black people, were still being bought and sold as slaves, decades after the Emancipation Proclamation freed blacks in the United States.
Those who want to "give back" should give back the truth. It is a debt that is long overdue.