The desire to persuade people isn’t necessarily rational, especially when it comes to “enlightening” people on the superiority of rational thought. I think a truly rational person’s allegiance should always rest in truth. Truth, in it self, is a very powerful notion that doesn’t need the help of manipulative persuasive tactics to inspire people.
I think persuasive techniques can be adapted to help discover the truth, as long as the parties involved completely respect each other and are willing to ask questions that help the other better articulate their perspective—they have to ultimately be on the same side and trust that there is rational thought behind each other’s statements, even if it’s not apparent at first.
As far as the Advertising example goes, I think I disagree. Advertising has become less effective because there is so much more of it. There are advertisements in more places than ever and and consumers are so used to seeing it that it’s hard to break through that clutter and grab their attention, especially in terms of the interruptive-based advertising model that is used on TV and in banner advertising online.
What might actually illustrate this point is the reason why advertising can be really horrible. It’s not that ad specialist have to signal their cleverness in a way that sabotages the end product by making it too clever, but more that people in the industry are constantly having to justify it’s quality to clients and colleagues—so they end up justifying things and approving things that are actually really bad.