Mr. Delong states:
It starts with an observation that we are all somewhat more interdependent than classical liberalism allows. It is not completely true that it is from the self-interest and not the benevolence of the butcher that we expect our meat. Self-interest, yes, but benevolence too: a truly self-interested butcher would not trade you his meat for your money but instead slaughter you and sell you as long pig. So this opens up a gap between the libertarian view and the world.
Perhaps Mr. Delong would slaughter his neighbor but I and most people would not. You see if I slaughter my neighbor then my other neighbors see what I have done. They are not stupid and they see what kind of person I am. Their most likely course of action is to try to make sure that I am either unable to slaughter them or unwilling to do so. I suspect that they would either wait for an opportune time to kill me or form a gang so that I would be fearful of killing them and they could take retribution if I did. The butchers good behavior is not benevolence in any sense but enlightened self interest. He knows that one course of action leads to strife and ruin and the other leads to peace and prosperity.