[The threat comes] … from men of good intentions and good will who wish to reform us. Impatient with the slowness of persuasion and example to achieve the great social changes they envision, they’re anxious to use the power of the state to achieve their ends and confident in their ability to do so. Yet… Concentrated power is not rendered harmless by the good intentions of those who create it.
Well first of all, tell me: Is there some society you know that doesn’t run on greed? You think Russia doesn’t run on greed? You think China doesn’t run on greed? What is greed? Of course, none of us are greedy, it’s only the other fellow who’s greedy. The world runs on individuals pursuing their separate interests. The great achievements of civilization have not come from government bureaus. Einstein didn’t construct his theory under order from a bureaucrat. Henry Ford didn’t revolutionize the automobile industry that way. In the only cases in which the masses have escaped from the kind of grinding poverty you’re talking about, the only cases in recorded history, are where they have had capitalism and largely free trade. If you want to know where the masses are worse off, worst off, it’s exactly in the kinds of societies that depart from that. So that the record of history is absolutely crystal clear, that there is no alternative way so far discovered of improving the lot of the ordinary people that can hold a candle to the productive activities that are unleashed by the free-enterprise system.
One of the great mistakes is to judge policies and programs by their intentions rather than their results.
[The threat comes] … from men of good intentions and good will who wish to reform us. Impatient with the slowness of persuasion and example to achieve the great social changes they envision, they’re anxious to use the power of the state to achieve their ends and confident in their ability to do so. Yet… Concentrated power is not rendered harmless by the good intentions of those who create it. 
Missing Reference