Some people get offended by the suggestion that humans should practice intensive selective breeding, they think it is only something for animals and they cannot get over their need for an emotional commitment to someone with whom they will have a child... many if not most people want to live with and love the person which whom they breed. But some people are the opposite, they are not opposed to using the science of animal breeding upon themselves and others... it is a personal value, and one which will soon divide the human race into those who have been honed by eugenics, and those who have not.
Most people would not want their dogs to be bred with genetic diseases and everyone knows that a dog's temperament is important in creating a desirable pet... dogs that have asocial personalities are excluded from breeding programs because we know that that personality can be passed on... but too many sentimental people refuse to understand that this same principle works in humans. Marital breeding is haphazard and is based on emotion, and emotion can cloud judgment. A woman or a man may become smitten by their partner's looks to the point that they overlook many detrimental mental flaws, or worse still some people are attracted to otherwise asocial people as they have a desire to nurture them. Many otherwise healthy bloodlines can become damaged by mating dependent upon lust or emotion.
However, eugenicists since the inception of the idea have lamented the "middle-class bias" of eugenics, desiring such things as good test grades and amiability, industriousness, and a positive attitude. While these traits are necessary for a stable society, it is also important to have the opposite end of the spectrum, people who might have a more malicious temperament. It would be hopeful that any selective breeding program would understand that the middle-class bias should not be exclusive... other otherwise deemed antisocial personalities should be considered. However, to those who are systematic enough to engage in selective breeding, it might be hard to overcome the impulse not to breed people who seem less industrious, less intelligent, more quarrelsome, and dependent. Indeed many eugenicists said that birth control was a good thing because the bohemian classes were availing themselves of it the most, but the more clever eugenicists said this was not necessarily a good thing, that we need eccentric people and shy people and ill-tempered people as well. The genius and enthusiastic eugenicist Nikola Tesla new that you cannot have a complete human without their weaknesses, their weaknesses help them excel into who they are, just as much as their strength.
Selective breeding needs to make many types of humans, humans in the same line would likely have similar personalities, traits, abilities, and preferences to some degree. In order for it to work, we would need diversity, and that means we would need scores of different kinds of bloodlines, and then we would need to continuously make new bloodlines by hybridizing different lines, this way we can always make new lines and also bring forth novel and unique humans. However, there is something to be said about random haphazard family building and acculturation. Random genetic mixing will produce humans that no selective breeding program could ever produce and sometimes dysfunctional families bring forth the greatest geniuses as they are detached from the norms of society and can think outside the box.
It would be foolish to selective breed all humans, actually, it would be foolish to selective breed most humans... selective breeding should be done by the few who can accept this system and want to engage in it, but there should always be random genetic and cultural material from which to draw from... new types of bloodlines always need to be drawn into the breeding system for undirected sources. This same principle applies to genetic engineering, it is probably best to leave the majority of the population natural. Only through this wisdom can a eugenic program truly work, the selectively bred need to lead upon a randomly bred population.