From the article:
The authors admit in their report that screening out narcissists, people who possess a morbid self-love or self-admiration, may deprive medicine of future leaders and innovators.
I work in the medical devices industry and this is SO TRUE! All the top surgeons (and even many of the bottom ones) are completely in love with themselves. There's even a joke that goes, "what's the difference between God and a surgeon?" answer: "God doesn't think he's a surgeon"
It takes a certain sort of personality to be able to cut someone open, and let their life rest in your skill. It takes an inordinate amount of self-belief, and the sort of mind set that isn't hampered if you kill or maim someone because you've made a mistake. I knew a girl who ran over a pedestrian when she first got her license; she never drove again. This woman would never have made a surgeon.
Doctors in general are more likely to be people who crave authority, who want respect to be due them. I think many in fact want the authority more than they want to "help" people (although one of my local GPs is excellent, and doesn't seem to have a scrap of arrogance in her -- I'm generalising wildly, but I do think it applies to a significant proportion of physicians)
If you weed out the most arrogant and self-loving medical school applicants, you would indeed deprive the industry of some of the top practitioners. And isn't it interesting that you almost never hear of such cases (ie like the Shipman case) involving nurses? That's because nursing doesn't normally attract people on power trips.