Particularly in light of NewJeffCT's comments re: word-count, I offer the following 199-word suggestion:
On April 2nd The Chronicle printed what I assume was an April Fool’s joke by Michael Oard, who argues that the biblical story of creationism is true. He declares that evolution is false without supporting this assertion, and his only argument in support of the Earth's young age is simply incorrect.
Mr. Oard reveals a basic misunderstanding of geology in asserting that North America would erode completely within ten million years, because he ignores the fact that active mountain formations provide plenty of new material to fill sedimentary basins. Additionally, he claims that there is no erosion within the Grand Canyon rock sequence and that a global flood is the best explanation. In fact the sequence displays at least seven unconformities, each representing a substantial span of time during which erosion occurs. These aren't explained by a giant flood, so how does Mr. Oard think they got there?
Mr. Oard’s errors don’t require advanced education to correct; one semester of basic geology is sufficient. If he is so sloppy with his facts in the one example he provided, what about his facts in the examples he omitted?
Even more worrisome is Chronicle’s choice to publish such tripe at all.
Mostly I kept your piece intact, but I compressed the wording here and there and retooled the bit about "unconformities" so that, I hope, it comes across as slightly less esoteric. I note that you used "supposedly" three times in a relatively brief piece, and this seemed a bit excessive (especially when word-count is important).
"Barnumesque" is a clever coinage but strikes me as a little too adversarial in this context. The essence of your piece is that Oard doesn't know what he's talking about, so you should focus the piece on him. If you intend to address the board's poor standards of selection, you should write another LTTE to that effect. Otherwise, it comes across simply as a petty, drive-by zinger.
I consider these suggestions to be your intellectual property; you are free to reject, accept, or rework them however you wish.