“Doctor Bashir, I Presume” makes the case that augments can be unstable and dangerous.

Two hundred years ago we tried to improve the species through DNA resequencing, and what did we get for our trouble? The Eugenics Wars. For every Julian Bashir that can be created, there’s a Khan Singh waiting in the wings. A superhuman whose ambition and thirst for power have been enhanced along with his intellect. The law against genetic engineering provides a firewall against such men, and it’s my job to keep that firewall intact.