Rhetoric is Inherently Evil

Another way to phrase Satan, Father of Lies, is the Devil, Lord of Rhetoric. All attempts to use rhetoric for good are self-defeating.

In theory you could use rhetoric to convince some idiot to be less idiotic. Rhetoric can, in isolation, be used to convince anyone of anything, after all. That's how it's usually so destructive. However, should you try this, they're not going to become logical. The wise actions will be rewarding, and they'll attribute that high to having listened to rhetoric, reinforcing the vulnerability. You'll find that the rhetoric they accept rapidly becomes inconsistent with wider and wider areas of prudent action. 

If you tell someone to save money because God, Lord upon High, likes it when you save money, they will also find that God, Lord upon High, likes it when you don't save money as long as you're giving it to a priest. Uh, oops. Clearly, he prefers this even to saving money. Rhetoric always works like this. All temporary gains come at the cost of long-term losses.

If you can, in isolation, use rhetoric for good, the truth runs as thus: "You're too dumb to run your own life and need to listen to exactly what I say or you're going to fuck yourself." This is not rhetorically effective.

Surely, you could use rhetoric to convince someone to become logical directly? Try the end run?
Lies are bad, mmmkay. It's kind of the point of a lie that they're illogical. No matter what rhetoric, what lie, you use to support logic, it's going to be inconsistent with critical components of logic. It's inherently and directly self-defeating. "Oh yeah, that was a lie I used to convince you to become more logical. Now you're ready to hear the truth. (Or am I only going to lie to you again and repeat this indefinitely?)" Fun fact: this is not rhetorically effective.