Strong disagreement -- your point sounds more weasely to me, to be honest. The situation as described is zero-sum; a talented youth leaving place A in favor of place B leaves the same amount of talented youth in the overall picture. If their departure is detrimental to place A, then the value that goes missing in that place does not vanish, it ends up in place B.

So, the point stands. If talented youth left the USA in significant numbers, would that be detrimental or beneficial to the USA? And you can feel either way about the answer there; however, you then can't have it different for talented youth leaving their own current home to bring their talent to the USA. Not in good faith anyway.

The problem here is that you allude to a vague definition of what is good - "the USA" is an abstract idea.

Is it the people living in the USA? The citizens? The State? The companies? The US stock market? A benefit for companies can be a big problem for citizens - environment, or privacy come easily to mind.

It is also context-dependent: is there a real unsatisfied need for skilled professionals in the sector that affects everyone in society (e.g in healthcare)?

Otherwise the added workers will just push down the wages for the other workers - but companies and investors may benefit, true. However, should a State policy be decided for the interest of companies against the citizens? Why is there even a need to vote then?

So yeah, oversimplifying a situation and then implying that if A is bad B should be true is sophistic, sorry. I could do the same, and ask if skilled immigration is good, why not remove quotas and let 3 million Indian ninja/x100 software engineers in per year.

If not, how much is the right quota? How do you define it? And you're back at the start.