That preaching is a persuasive act, means it will be undervalued in contemporary cultures where diversity of perspective and self-definition are the most highly prized qualities. People typically are not interested in being persuaded to adopt the preacher’s perspective when the culture celebrates the expression of their self-derived convictions.
In such a setting, I found it helpful to review what Blaise Pascal had to say about persuasion in his Pensees.
When we wish to correct with advantage, and to show another that he errs, we must notice from what side he views the matter, for on that side it is usually true, and admit that truth to him, but reveal to him the side on which it is false. He is satisfied with that, for he sees that he was not mistaken, and that he only failed to see all sides. Now, no one is offended at not seeing everything; but one does not like to be mistaken, and that perhaps arises from the fact that man naturally cannot see everything, and that naturally he cannot err in the side he looks at, since the perceptions of our senses are always true.
Pascal offers an appreciative form of persuasion, respectful to the listener that he is seeking to persuade. Far from mere flattery, Pascal looks to build upon whatever is objectively true within the listeners’s self-expression. It may be that the listener is not particularly bothered by the need to think congruent to the truth. Nevertheless, by asserting what is actually true within the listener’s perspective, the preacher encourages the best impulses of the listener’s mind, while charting a more helpful, more consistent, and ultimately more truthful path for the listener.
This form of preaching, while being more winsome, cannot help but be more persuasive.
For further reference, have a look at this brief piece by Maria Popova of brainpickings.org