Actually, Butler, Walter Block wrote about the profession of pimping in Defending the Undefendable (pages 9–11 in the book itself, not the pdf file pages). Pimps—like the prostitutes who they employ—also offer a voluntary* service, unlike the criminal politicians who are forced upon us through the forced monopoly of force called government.
_____________________________
*Unless, of course, the pimp is keeping the prostitute against her will and/or physically abusing her.