I have been unable to track down the paper, but a recent study demonstrated that listener comprehension was higher when filler words were used during speech.
I think they are stigmatized because often they are used heavily by those who have no idea what they are taking about. But the fix is to know what you are talking about rather than to eliminate 'umm' from your vernacular. These pauses give your audience time to think, give your audience cues on what parts are important, and let you pull together your own thoughts.
Only in his unscripted communications. His reputation as a speaker stems from his delivery of messages that are usually pre-written. He's got plenty of dramatic pauses where normal people would say "ummm".
He's considered a good speaker when he is rehearsed. He is considered an umm-er when he is speaking candidly by anybody who doesn't also speak like that.
In his defense, everything he says is hyper-analyzed so he does have to be more careful than most of us.
I think they are stigmatized because often they are used heavily by those who have no idea what they are taking about. But the fix is to know what you are talking about rather than to eliminate 'umm' from your vernacular. These pauses give your audience time to think, give your audience cues on what parts are important, and let you pull together your own thoughts.