I wish it were as simple as "endorse BS, lose credibility forever". Unfortunately, this industry simply does not work that way. You see, Mr. Greenfield has very low body fat and visible abs. This confers credibility in a way that is very hard to overestimate. Mr. Rippetoe can write an article insisting, for example, that strength is more important for healthy aging than low bodyfat, argue his point cogently, refute its counter effectively, point to many years of clinical data that supports the position, and under that article commenters by the dozen will insist he couldn't possibly know what he's talking about because he's got a gut.
Additionally, when one endorses some piece of equipment or some methodology or some movement screening tool, making significant-sounding claims about the efficacy - and it turns out to be snake oil once actual science has had time to evaluate the claims - the next move is to fight a rear-guard action, claiming the science didn't test your actual claims, and anyway we've refined our approach far beyond what was tested by this obsolete research paper. Thus, the FMS can fail to predict athletic performance in scientific testing and be shown to predict injury risk almost exactly as reliably as a coin flip and people will still rush to its defense, simultaneously insisting it never claimed it could predict such things while ballyhooing the upcoming updated version.
