The cornfield comment was either a reference to Bob Dylan's rural upbringing or a Twilight Zone episode

Absolutely nothing racist about that or his comment. Is it really a stretch to imagine that someone who made "Starships" and "Stupid Hoe" might not be appreciative of singer-songwriter rock folk music?
Nicki misinterpreted and made a mountain out of a molehill. He didn't need to apologize or retract anything or explain himself.