Jackson's "all men are corruptible and weak" theme was stupid and the worst part about the film trilogy as a whole. Faramir has plenty of interesting issues to deal with as far as his personality is concerned without having to introduce a corruptibility that isn't supposed to be there. Theoden, Wormtongue, Denethor, and Boromir (not to mention the Nazgul) all clearly illustrate the weakness and corruptibility of men. Aragorn, Eomer, and Faramir all show that those aren't universal and unavoidable characteristics of mankind, and Faramir is the most effective illustration because of the failings of his family.

You aren't the only one who has studied writing and storytelling, so don't take the "I am a writer so I know more" line. It's fine that you have that opinion, but I disagree thoroughly with your application of your position to this particular story and set of characters.