The "Guardians of the Galaxy Vol. 2" helmer defended the casting in a lengthy Facebook post published following the social media backlash from fans, reported Ace Showbiz.
"People get upset when something they consider intrinsic to a comic book character changes when adapted for a film. I get this," Gunn said.
"I do not believe a character is the colour of his or her skin," he added, before addressing the reports about MJ being played by the young black actress.
"For me, what makes MJ MJ is her alpha female playfulness, and if the actress captures that, then she'll work."
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Gunn also noted that he was speaking hypothetically as he couldn't confirm the casting report.
He added, "Whatever the case, if we're going to continue to make movies based on the almost all white heroes and supporting characters from the comics of the last century, we're going to have to get used to them being more reflective of our diverse present world.
Jon Watts' "Spider-Man: Homecoming" released on July 7, 2017. In the upcoming film, Zendaya stars alongside Tom Holland, Robert Downey Jr. And Marisa Tomei.