George Capsis, 86, told Sky News that he had not followed the advice of his staff, who had all warned him not to use the racist term.
"He (Collier) did not realise how loaded that word was. He was very proud of what he did. He thought any black who read that article would say, 'how brilliant, how sympathetic, how intelligent you are'," Capsis said.
"He wanted to demonstrate that there were still these extreme, hateful, unthinking, unreasoning voices out there."
He went on: "My staff were vehement. I thought that they were wrong. Now in retrospect I realise that I was wrong. You just can't use that word anymore, even if you are on the right side."
Capsis added that the article directly below Collier's, which was written by African-American columnist Alvin Hall, had been commissioned as a "rebuttal" piece.
Underneath the leader "The Headline Offends Me", Hall wrote: "For me, just seeing the n-word in a headline or in an article always makes me bristle. I feel a knot of indignation, disgust, and anger form in my gut."
Capsis said: "Alvin had an immediate, convulsive reaction to the headline, which goes right to his spinal column. He reacts with fury, electrically, and immediately dashes off a piece."
But Capsis admitted that having Hall's piece next to Collier's was not enough to justify the use of the n-word.
"Even the most liberal of liberals can't use that word if he is not black. The word itself triggers such a deep emotional and traumatic response that reason is gone," he said.
- UK Independent