Well, there are two issues in my post. 1.) Is the Paleo diet legitimate, and 2.) Is it attracting some douche bag followers.
The answer to the question of whether the movement is attracting idiots is, as evidenced by this article, a clear yes. This is shown in silly comments like: “Another caveman trick involves donating blood frequently. The idea is that various hardships might have occasionally left ancient humans a pint short.”.
The answer to whether the diet is legitimate is I don't quite know. My suspicion is there are things to learn from it, but let's not forget, we aren't cavemen anymore.
The big question for me is does the caveman diet (and there are more than one at this point) work without the caveman lifestyle, and that really would require long term studies, not anecdotes, which is all we see so far.
That being said, it's almost certainly better than the highly processed food most Americans eat right now, but that hardly makes it a first choice for a diet.