This is really funny: "How To Argue With A Libertarian." Perhaps the statists should take some lessons!
4. Criticize capitalism by its worst cases. But do not (ever!) compare these to the worst cases of statism.
Example: "The Enron scandal was the product of unfettered profit seeking under capitalism." If a libertarian replies that Stalin's brutality was the product of a statist program, change the subject or claim that your brand of statism precludes such abuses. Better still, try to argue that Stalinism was actually a kind of capitalism.
Thomas Woods makes an excellent point in "Are Capitalists Bamboozling the Poor?" He discusses a fact that never fails to come true in statist propaganda: whatever improvement to the quality of life of the poor brought about by the market, people will oppose it vociferously. Statists hate no one more than the poor.
For lack of a better term I am dubbing it Woods's Law: whenever the private sector introduces an innovation that makes the poor better off than they would have been without it, or that offers benefits or terms that no one else is prepared to offer them, someone — in the name of helping the poor — will call for curbing or abolishing it.