Remember Churchill was half American. I can recall when it was regularly suggested that Churchill was one of the greatest men of all time.
Churchill was an ardent defender of freedom. It is only natural that a socialist quasi marxist (I am not sure about the quasi) does not want a bust of Churchill in the oval office.
Just like the Messaih. Both of them had fathers who were UK subjects. Maybe he fears that it will remind others, or just doesn't like the reminder himself?
He won the “100 greatest Britons” poll in the UK a couple of years ago hands down.