I agree. The problem is once the genie is out of the bottle, you can't rely on every nation-state and every organization to adhere to any consensus about the use of genetic engineering.
In an ideal world, humanity would be scattered and numerous enough that the engineering of any one population would leave the others unaffected. But as it is, we're all stuck on Earth in a global, interconnected civilization without central authority, so once this technology is introduced, the incentives are aligned against us.
But I don't know what else to try.
> even if that class lacks genetic diversity, that seems like exactly the kind of issue that genetic engineering exists to solve.
Why would anyone choose to have genetically diverse children if that diversity led to immediate short-term problems? Who would bite the bullet and have 100IQ child who had to compete in a world of 150IQ children for the sake of genetic diversity?
welcome to the new arms race.