Their parents I would think or until they are able to provide and sustain themselves on their own. Anyway, this is a really weird kind of argument you've gotten yourself into. It completely misses the intent of the post.
Fortunately when people can look at issues rationally not emotionally we can debate under what conditions (age, development, maturity etc.) a person is able to give their consent.
Once everybody in the world is considering issues rationally the first guy that starts debating emotionally is going to have a hell of a big influence. Half the population has an IQ below 100.
But if everyone in the world considered issues rationally, then everyone would be smarter, no?