Why should child labour be banned?

Pollution can be solved by private property rights. Pollution that injures others is aggression.

Anti-trust laws are useless.

In a free-market system, corporations cannot wield political power and influence policymakers through lobbying or campaign contributions. A company can only grow by serving their customers effectively and efficiently. Harmful monopolies cannot form in a free-market economy. 

 Have to disagree on this one… seems to me that monopolies could certainly form in a free market economy 

 I never said they couldn't. I said that harmful monopolies couldn't.