I saw a contradiction

Context
I am currently reading Acres of Diamonds, a speech given by Russell Conwell, the founder of Temple University. I'm reading it in book form, and on page 41, Conwell tells a story about John Jacob Astor's success coming in small part because when he owned a hat shop, he only sold bonnets copied from ones he had seen contented ladies wearing. Then, on page 47, Conwell talks about how important great inventors are in a capitalist society.

Commentary
Acres of Diamonds is a polemic extolling the virtues of making money, almost to the exclusion of all else, so I'm probably predisposed to pick it apart. It was funny though, I read the Astor story and said to myself, "So Conwell is saying innovation is bad." Then I got to page 47 and thought, "Unless it's a successful innovation that makes money. Then he's saying it's good!"

I think this odd juxtaposition struck me harder because earlier this week I was in a two-day workshop where I thought the consultant contradicted herself repeatedly. In fact, there were enough instances that I thought I could develop a pretty good drinking game based on them, but you know how punchy you get at these things.

Anyway, these two sets of circumstances got me thinking about why people contradict themselves and why we as listeners sometimes don't notice. I came up with two reasons:

1) Someone is presenting so much information that contradictions kind of creep in unnoticed. I think this is applicable not only to Conwell, who seemed to want to say everything good about capitalism at once and the consultant, who was trying to fit a great deal of material about library planning into two days, but also the world in general these days, where so much information is available that it's hard to take a moment and realize that "A" cannot exist in the same universe as "B." I think we should pay attention if this is happening, and you can count on The Daily Show to point out as many of them as they can get their hands on, but morally the phenomenon is pretty benign.

2) Someone is so intent on making a point that they will use whatever arguments are at hand, even if they make no logical sense. This is not so benign and nearly impossible to combat. It is the argument that starts with, "We know President Obama is not a citizen because he can't produce a birth certificate," then decides to cover all bases with, "The birth certificate President Obama has showed people is falsified."

My concerns about #2 are, I think, why I'm picky about internal contradictions in a presentation. If you're trying to convince me of something, I want all your arguments to line up and make sense. Otherwise, I just think you're trying to sell me something.

What did you see today?