That's purely a "guideline" of common sense. You wouldn't say, "Don't support laundromats that murder senior citizens", would you? And as far as I know, travel agencies usually only advertise package specials and Michelin guide ratings; I don't think that in all my years of travelling I've ever come across one that advertises pedophila packages. Keep in mind, that "child sex" is a vague term. For instance, in the Czech Republic, the age of consent is 14, and other countries have similar laws. While some people in America may find this despicable, it is important not to be culturally myopic and understand why certain laws exist for certain countries.