I don't have any personal experience with the fellow (or in-truth the kind of courses he offers) but I do have some experience with the mindset he has. The article in question relates to situational awareness, and he occasional propensity of people who either should know better, or at least present a front of should have known better to be less than attentive.
Mr Mosby has some honest opinions around people's physique that I might not have expressed the same way, but he's entitled to his opinion and probably knows better when it comes to the physical requirements and standards certain callings should have. This said, I find his observations on people's behaviour very telling.
I may well be one of the gear-collecting, Dungeons & Dragons playing types who needs to do more realistic training fundamentals well before I move on to being a Delta Force, Ranger, MASOC operator, but I think we can all agree, we could all do well to "hone the edges on your ax."
Me in D&D mode.