This is completely missing the point. It seems some have interpreted "incompetent" in another way than it was meant. It is not meant to be degrading. It is used to be able to discuss how we perform on different skill sets compared to peers. Some of us are better at one thing and others at another. The mentioned study acknowledges that and uses the words competent and incompetent to rate a group of people within a particular area of skills. Competent or incompetent is used to compare the individual to their peers based on a particular skill set. It doesn't imply at all that someone is incompetent in other area, which is how some of the replies seemed to interpret it.
In other words, sure Einstein was a genius in physics, but I doubt he was a good baseball player. So in that case we can call Einstein an incompetent baseball player.