The phrase wasn't even coined by him. You can find it in literature text books going all the way back to the turn of the century. Hell, it is even used in reference to black figures all throughout world literature, not just here in America.
The columnist didn't coin the phrase "magic negro." but I think what Catz is referring to, is that the columnist did write "Barack the Magic Negro" ... or ... "Obama the Magic Negro" first. or whatever it was.