You're making a mistake - one I'm not making, by the way - in confusing the symbol for the philosophy, the trappings of power with the perversion of it. The presence or absence of swastikas in Korea (or anywhere else, for that matter) is immaterial. If you paid attention to the links I posted, you'll have learned that the Nazis were not the only practitioners of "eugenics" - sterilization in the name of "improving the species" was, briefly, carried out in the U.S. and Canada.

The question remains: Who decides who will be permitted to breed, and who not... and why?

Because you know - or should - that so-called "positive" eugenics, such as ordering certain desireable traits from a catalog before conception, will not be the end of it. Pressure from the enhanced, and those who wish to be, to eliminate "undesireable" traits from the gene pool will soon follow.

There are scores of writers who have thought through hypothetical scenarios of this kind. Since you seem not to "get" Brave New World, I suggest any and all of the following as a way to open yourself to the possibility of other views on the matter:

Beggars in Spain, and its sequel Beggars and Choosers, by Nancy Kress;

Darwin's Radio, and its sequel Darwin's Children, by Greg Bear;

Odd John, by Olaf Stapledon.

Be sure to pay close attention to the backlash among the un-enhanced.