/Soapbox on
Doesn't the article state biblical time scale?
I think that means that the book's author is trying to say the grand canyon was created in a sudden 'geologically speaking) series of events, as opposed to the generally accepted explanation for its origin. Now, you (and I) don't have to agree with his interpretation of events. But we should defend his freedom to express that interpreation, regardless. The book, along with many others, is offered at museums and bookstores. It's not as if it's being endorsed as the only possible 'truth' by the park service.
Dumb people trying to promote their religious agenda in a book that makes no sense to anyone who looks at the facts obejectively should not have their works banned from stores.
That's suppression of stupid people. If we're going to do that, I'm all for it. But I get to decide who's stupid and how to suppress them (a bullet, perhaps?).
As it is, you can expect this author to be economically suppressed for putting something so outrageous in writing and asking people to pay money for it.
The article also indicates that the plaques were sponsored. I'd assume that indicates anyone could sponsor a plaque with any sort of inspirational text on it, regardless of the source and that only those plaques with biblical quotes were removed in the first place.
THAT sounds more like religious suppression than separation of church and state. The idea is that the state should have no opinion on the subject of religion, provided that a religion does not interfere with the state.
Plaques at parks sponsored by individuals who pay for them don't unduly influence the state.
/soapbox off
We can't just let the politically correct people have freedom. It has to be everyone.