The 56-year-old singer now took to Facebook to defend her action and said those pics were never intended to insult anyone, reported TMZ.
Madonna posted a series of black-and-white pictures on her page on January 2, showing the faces of Mandela, Luther King and various icons bound with black string.
"This is neither a crime or an insult or racist," she posted on the social-networking site.
"I'm saying they are Rebel Hearts too," she added.