In Defending the Undefendable, Walter Block defends the heroin dealer, the speculator, the employer of child labor, and the man who screams "fire" in a crowded theater against accusations of economic perversity and harming the social order. He does so quite effectively. After reading this book, one who is educated in economics will have to seriously reconsider support of a minimum wage and legal prohibitions against child labor.
The introduction, written by Rothbard himself, makes it clear that while the people defended in Block's book are heroes because of the role they play economically and the adversity they face in reducing the friction of a politically-controlled economic system, this is not a moral defense of the particular actions the people make. For instance, a heroin dealer could very well be a boon to the market and a hero in face of the evils of government while also perpetrating an immoral or unethical act (such as selling poison to people, even if it is a voluntary interactions).
As compelling, concise, and informative as the book is as a whole, there is one chapter, however, that doesn't seem to belong. The defense of the "Male Chauvinist Pig" was less an economic defense of chauvinism and much more an incoherent and aggressive defense of feminist talking points, most prominent of which being the importance of abortion. This defense of abortion is actually inconsistent with a much more compelling case he makes later on in the case of defending "The Employer of Child Labor".
All-in-all, though, this book is a must-read for anyone who believes in the free market but hasn't critically assessed their position on "the undefendable" as of yet, people who are genuinely interested in reducing crime and increasing the quality of life for the poor, and those that still believe that government violence can somehow improve the world. Each chapter is a few pages long, very direct and to the point.
One can acquire the book for free in digital form from the Mises Institute, or purchase a hardcopy at Amazon. I strongly recommend that you do so.