There's so much wrong with that quote that it deserves a separate post in and of itself--
Capitalism is based on private property. Acts of stealing are, by definition, anti-capitalist. What Blackwater did is just what socialists and thugs all over the world have always done - 'redistribute' the wealth. It isn't capitalism.
Capitalism is fair in that all it takes to get ahead is money and possessions, and everybody is allowed to get or have these through legal means. Capitalism is unfair in that we don't all start out in life with the same amount of money and possessions, and hard work alone can only get you so far through legal means if you start out with a bum deal.
(one, since when do "socialist thugs" have listings on the nyse and nasdaq exchanges (?) two, blackwater guards aren't there to "redistribute" they're well paid...they're there to terrorize and murder the populace (usually intellectuals, college professors, and yes atheists get the gun), a salient trait from every core capitalist authoritarian regime from Nazi Germany to Chile in the70s to El Salvador in the 80s and most places where regime change has been orchestrated by the United States. Every fascist regime needs its SS.)
--but your textbook definition of capitalism is nicely deconstructed and its horrific implication nicely drawn out by the author of "The Story of Stuff". Uncle Scam has already posted part of it in the previous post but here's the whole thing from Google Video. By the way, if you or your friend Greg choose to rebut it could you watch it? Trust me it helps form the rebuttal.