That argument makes no sense. We have to measure people? Really? Why? If his claims are correct, then Gladwell is right -- we're doing worse by screening people according to criteria that are useless, because we're essentially randomly filtering out a large percentage of the people who are good at the job.
You can attack the evidence for his claims, but if the evidence holds, then the conclusion Gladwell reaches is a logical consequence.
I'm sympathetic to his claims, as I went to a crap school and got a crap GPA. Okay. I'd love it if people had judged me based upon my winning personality, my good looks, or my tendency to point out everyone's foibles, but I'm not sure those are a superior measure of coding skill... Even if they were, they could be subjected to analysis and so become objective measures themselves.
The practical reality is that lots of jobs have 1000s of aspirants. How many kids want to play in the NBA? MILLIONS. You need something to divide them up, and if one objective measure is genuinely bad, it needs to be replaced by a better objective measure.
If the "objective metrics" are useless discriminators, then the only effect of using them is to make us feel as though we have control over a situation that we don't understand. In that scenario, it makes far more sense to restructure the game to allow more initial participants, and to cull the best players.
You seem to be arguing that we must have "objective" filtering mechanisms, even if they're random. Gladwell is saying that the whole paradigm is wrong.
You can attack the evidence for his claims, but if the evidence holds, then the conclusion Gladwell reaches is a logical consequence.