It might be stuff like an increased cultural focus on some genetics being "better" than others. Or an increased genetic divide between the rich and the poor over generations. Or unintended consequences where we make mistakes and cause new diseases or problems for the people that are being genetically modified.
But the chance of governments intervening in this seems low, other than maybe to require people to not select for bad traits or to put more restrictions on this technology (as many have already done).
And the idea of genetically engineering an under-class is equally absurd. Who would buy-in to that? It’s so obviously ethically evil. If we live in free countries with free press, this is just not going to happen.