Griffin's Ridiculous Cumulative Argument

One of the more annoying claims of David Ray Griffin is that he presents a "cumulative argument". He explains during a debate with Chip Berlet on Democracy Now from a few years ago:

The main point, as I made -- stressed in the book and stressed earlier today is that what I have presented is a cumulative argument which relies on a massive amount of evidence that I do take to be prima facie reliable in the most part reliable as main line sources. I stress that what I'm making is not a direct charge, but a prima facie charge that says if these facts are borne out by a further investigation, then we do have strong evidence of complicity. With regard to what he said about a couple issues, I pointed out in the book that if you're presenting a deductive argument, that's when we say that no chain is stronger than its weakest link. Then it is important to point out if there are a couple premises of the argument that are at fault, then the whole thing falls. But with the cumulative argument that isn't the case.

As I understand it, the argument that Griffin is making is that if individual pieces of evidence do not rely on each other but are independent, then demolishing one claim does not destroy the entire argument, but just that one claim. In terms of logic, it is the difference between "and" and "or". If the argument was built on a chain of evidence, it would take the form of "If A and B and C and D, then 9-11 was an inside job." What Griffin claims is that his argument is "If A or B or C or D, then 9-11 was an inside job." And therefore, disproving A is not sufficient to disprove the conclusion; we have to disprove A, B, C and D.

In terms of logic, he is on sound footing. But in reality, it's a stupid argument for stupid people. Why?

Let's consider an example. Some parents come home from an evening out to find that a sixpack of beer is missing from the refrigerator. When confronted with this, their teenage son claims that "Maybe Joe took it." But when the parents check with Joe's folks, it turns out he's a couple hundred miles away at band camp. So the teenager tries, "Maybe Sally took it." But Sally's been ill and hasn't left the house for days. So now the teenager tries, "Maybe it was Barry Bonds or Carol Burnett or Mahatma Gandhi." When the parents point out that Barry's team played this evening in Los Angeles, that Carol Burnett does not drink, and that Mahatma Gandhi is dead, the teenager comes up with a list of 50 other people who could have done it.

Do the parents check that list? Of course not, because there's a little thing called credibility, which their teenager has already used up. This reveals the absurdity of the "cumulative" argument. Griffin would apparently argue that the parents must eliminate the entire world before they have proven that their son took the beer, and in a strictly logical sense he is right, but nobody behaves that way in real life.

The cumulative argument encourages BS and laziness on the part of 9-11 researchers. Do they have to be cautious and carefully consider whether evidence fits or makes any sense? Nope, because in Griffin's mind, there is no penalty for being wrong on any one item, no loss of credibility suffered.