The drama, which is set in ancient Egypt, has a predominantly white cast with non-African actors in lead roles.
Christian Bale from Wales has been cast as Moses whilst Australian Joel Edgerton plays the Egyptian Pharaoh Ramses.
Social media has seen growing criticism of film makers Fox.
But Mr Murdoch, who runs the company, posted a number of tweets rejecting the complaints.
"Moses film attacked on Twitter for all white cast. Since when are Egyptians not white? All I know are," he said.
But when his tweet was accused of being racist he replied: "Everybody-attacks last tweet. Of course Egyptians are Middle Eastern, but far from black. They treated blacks as slaves."
The he tweeted: "Okay, there are many shades of color. [sic] Nothing racist about that, so calm down!"
The film will be released later this month.