FDR's approach to dissidents was to invite them to the White House and treat them to a barrage of charm and awe. He was sublimely good at that, and disarmed most people who dared talk back to him.
Could you please cite evidence for this?
I reccomend you read anything about FDR's campaign against Hoovr in the early 30's. The anecdotal evidence is huge, and very entertaining (if a bit creepy).
Oh, you might have to go to a library to do this. Don't be afraid, it won't be scary.