Sure, it doesn't need to be related to the Paleo diet, but that's still where it all stems from. It's the same as any other fad diet or pseudoscience: Come up with some reasonable-sounding claims that take advantage of poor scientific awareness (e.g. 10,000 years isn't enough time for humans to adapt to eating grains, so we should eat like cave men instead), then make millions of dollars promoting your diet and selling books to your unquestioning followers.
There's a common sentiment among Paleo zealots that they finally need to distance themselves from the irrational underpinnings that started the whole fad (see here[1] for a FAQ by the 'Paleo diet' inventor). The problem arises when they go searching for scientific evidence to support their grain bashing, and then we end up with statements like this:
> It can stem from the simple proposition that fruits and vegetables are generally healthier to eat than grains. That’s an argument I’ll cover more deeply in later posts.
Oh, how convenient. Save the crux of the argument for another time. We'll all be patiently holding our breath.