But that isn't how it is. Someone who says "um" a lot while speaking doesn't sound stupid. They're grating, to many in the audience, but that doesn't reflect on the speaker's ability (except, obviously, their public speaking ability). That means the audience will be focusing on the speaker's verbal tics instead of the message that was intended, which is the root problem. The word "stupid" was intended to startle the employee into action by how rude it was.

I mean, obviously, in this particular instance with this particular person, it was effective, and for all I know, the manager is a really sharp observer of her reports and knew this was the right approach in this situation. I don't think it's a good general approach, and I'm afraid people are going to take away the wrong thing from this article. It's not good managerial advice to say, "Tell your employees they sound stupid if they are bad public speakers!" It's better managerial advice to say, "Know your employees, and how each individual might be best motivated, and don't accept complacency." You have to be really careful when taking cues from drill sergeants, because for a lot of people, that approach will backfire horribly, and the message will be overshadowed by the delivery style.