I remember reading about what side of the brain controls what a while back. I posted a test on just about every web sight I posted on at the time. I don't keep to one ideology when I pick the places I go to. Liberal, Conservative, Theocratic and Atheist. Heck I have a membership at an anarchistic site. Everywhere I posted that test the results were the same. People used equal parts of both hemispheres of the brain. I think this guy is trying to stretch something he doesn't understand to fit his view of secular people.
I've been in 4 secular sites and all have had their fair share of people registering to quote/unquote show us the error of our ways. I think this is much more to do with intolerance that anything that even remotely intellectual. He just found some little issues that he thinks he can make his hijack to promote his own agenda. Kind of like what the churches have done with religion.
Yes, I think it's related to the 10% myth, but I can't prove it. People think that just because the left brain controls the right side and the right brain controls the left and that each hemisphere is assigned specific actions, such as speech and language, and that that is all there is to it, but it's far more complicated than that. I think even Buddhists monks, esp educated ones, know better than that.