It all started when Steven Tyler said this in an interview with MTV:
"These kids, they just got out of a car from the Midwest somewhere and they're in New York City, they're scared to death; you're not going to get the best [out of them]. ... If it was Bob Dylan, Nicki Minaj would have had him sent to the cornfield! Whereas, if it was Bob Dylan with us, we would have brought the best of him out, as we did with Phillip Phillips. Just saying."
Then Nicki got her rage-tweet on: