Spec i agree Olympic is a country based sports competition and a poor choice of analogy.
Nobel prizes (even with all their controversies) probably represent a better choice. They do not have country based limitations, so if an American physicist wins the award it does not mean that an American Chemist or Biologist can not. Even for selection of best physicist there is no limitation that all the top contenders can't be from a single country. The idea is to pick the best physicist.
There is an alternate (and interesting) way to look at Olympics as well. Even Olympics does not limit the number of Golds (or medals) a country can win. Let us apply current USCIS policy to Olympics and see how it will look.
Assume only three games - Tennis, Swimming and Volleyball. USCIS will allow any number of entries from a country in each game (unlike the current Olympic policy), but it will cap the golds a country can win. So if US wins Swimming and Tennis its Volleyball team will be denied a medal even if it were the best.
Compare a GC (and the underlying job offer) to a medal (only for driving the point, i know the difference in stature !!!). There are three organizations - Intel, Boston Medical center and Citigroup. Any number of people from any of the countries can apply for these jobs. But if Intel and Citigroup have hired an Indian, then Boston Medical Center is forbidden from having an Indian doctor even if he is the best for the job.
Logic can often be twisted to arrive at results that we beleive in anyway

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Keeping diversity as an immigration objective is not necessarily wrong but its impact on skills based categories certainly does not seem right.