I can say it more simply :-)
Utopians and leftists in general want to implement Plato’s Republic, with themselves as the Guardians, their hired henchmen as the Warriors, and the rest of us as the Workers.
Conservatives in general want to implement Aristotle’s Politics, sometimes as amended by Locke’s Second Treatise on Civil Government, with a check-and-balance of power between the oligarchy and the citizenry—in other words, a true republic, not a Plato’s Republic.
Most people in general do not care what the government is, as long as it is there when they think they need it, and not intrusive when they think they don’t need it. This is why leftists can con them into thinking that they (the leftists) are the only ones who care about them, and that conservatives only care about themselves.
This is also why Trump is going to win, because for the first time since Reagan we have a standard-bearer who can convince the general populace that he cares about them, and that Hillary doesn’t. The leftists will figure that out some time between now and 2020, and (if they are smart) find a candidate for the next election who exudes caring, as Obama did in 2008, as Bill Clinton did in 1992, as Carter did in 1976.
These things are meritocratic in concept but never turn out that way in practice because the model simply doesn't correspond to actual human behavior. For example, one solves familial tendencies - what father wouldn't want to see his sons succeed? - by eliminating the family altogether after one or another elaborate educational mechanism. And it fails. For another, they tend to insist on optimizing production around what people do (or are perceived to do) best rather than what people actually are happy doing. Marx was a firm opponent of this and his systems in practice turned out to be major proponents of it, because "from each according to his ability" was coercive and not, as Marx hoped, a case of human self-actualization. And for a third example, under his systems the state didn't melt away as it was supposed to, it grew, because running a state turns out to be a prime gig.
These are all fatal signs that these models of a planned society are inadequate to the complexities of human behavior, and that only human vanity insists that still they be implemented. That vanity, as Greenfield points out, is resident in those convinced of their own personal superiority and hence ability to direct their societies at large. Let's look at facts: the ubermenschen turn out to be a dime a dozen and frankly, they aren't all that great.