Adam Grant writing in the Atlantic on the power of emotional intelligence over an audience. In many cases, the audience leaves an emotionally crafted speech with a sense of satisfaction and strong recall of the content. When questioned, however, it turns out their ability to reason and recall was actually impaired:
In emerging research led by University of Cambridge professor Jochen Menges, when a leader gave an inspiring speech filled with emotion, the audience was less likely to scrutinize the message and remembered less of the content. Ironically, audience members were so moved by the speech that they claimed to recall more of it.
The authors call this the awestruck effect, but it might just as easily be described as the dumbstruck effect. One observer reflected that Hitler’s persuasive impact came from his ability to strategically express emotions—he would “tear open his heart”—and these emotions affected his followers to the point that they would “stop thinking critically and just emote.”
The preacher must always beware of the power of words for life and death (Prov 18:21). Moses and Paul exemplify two prophets whose communication skills were not their best parts, and still the Lord used them to gather communities to his word. For his part Moses may have had a speech impediment (Exod 4:10), and Paul admitted to eschewing persuasive style for the simple message (1 Cor 2:1).
According to this article, the problem with abusive emotional manipulation is that your congregation may thank you for it.