From the Libertarian Platform
Governments throughout history have regularly operated on the opposite principle, that the State has the right to dispose of the lives of individuals and the fruits of their labor. Even within the United States, all political parties other than our own grant to government the right to regulate the lives of individuals and seize the fruits of their labor without their consent.
We, on the contrary, deny the right of any government to do these things, and hold that where governments exist, they must not violate the rights of any individual: namely, (1) the right to life -- accordingly we support the prohibition of the initiation of physical force against others; (2) the right to liberty of speech and action -- accordingly we oppose all attempts by government to abridge the freedom of speech and press, as well as government censorship in any form; and (3) the right to property -- accordingly we oppose all government interference with private property, such as confiscation, nationalization, and eminent domain, and support the prohibition of robbery, trespass, fraud, and misrepresentation.
Since governments, when instituted, must not violate individual rights, we oppose all interference by government in the areas of voluntary and contractual relations among individuals. People should not be forced to sacrifice their lives and property for the benefit of others. They should be left free by government to deal with one another as free traders; and the resultant economic system, the only one compatible with the protection of individual rights, is the free market.
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Nowhere in this platform is a child defined as anything and it doesn't require "evil" to assume that a child would be defined as an individual according to this ideology.
Additionally, as I stated, libertarians seem to have short memories and don't remember the abuses, even beyond child labor, that were addressed and solved by the COLLECTIVE, not individuals, and not the free market.