It has to be controversial in a way that compels people to research/learn for themselves. Do you really think he could directly say or do anything that his detractors would not immediately pounce on and call 'political', 'lies', or just plain stupid ol' Drumph ?
He provokes - he asks dumb questions. Go find an old episode of Columbo and you'll begin to understand. He makes some people think, and he makes other people out themselves.
He cant possibly make this any more obvious - not even if he picked up the phone and called you up directly to explain it. Think, anon. Think.