Our discussions of AN iv.128 ff and of the importance of direct oral
instruction are now, I believe, beginning to converge.
In the passages we've translated so far, the Buddha has instructed
his listeners firstly on the dangers of sexual incontinence, and
secondly on the dangers of fawning before the wealthy.
I would say that what he's doing here is applying the "sa.mvega
technique." He is inducing in his audience "sa.mvega" -- a rousing
toward spiritual effort, often brought on by a sudden or horrific
realization that propels one in the right direction.
Even the Buddha himself had the sa.mvega experience: