A better way to approach the Paleo hypothesis is as just that -- a hypothesis. I think all reasonable people agree that humans have changed somewhat since paleolithic times (and grains were possibly part of our early diet) but it still seems quite reasonable to posit that 1) our diet has changed greatly since the longest period of human evolution and 2) it may well be more healthful to return to a diet closer to the paleolithic diet. That's a reasonable hypothesis that can be tested.

Of course that's not the way the popular press and fitness industry approach the Paleo diet, but one shouldn't throw out the baby with the bathwater.

Yes. The Paleo diet might even make sense for humans, but their justifications can be pretty rubbish.