>adult wants to have sex with a child
>child agrees
>despite both parties being willing we have as a society determined that due to the potential consequences of this on the child and the fact that the child doesn't have the necessary experience, knowledge and/or a developed enogh brain to make such a decision for themselves, even though they do have a conciousness that says "yes" his anwer always defaults into a "no" because they lack the ability to make an informed decision
>this is accepted by most societies and you will be called a freak for questioning it
all good so far

>adult wants to have a child
>child cannot agree as it doesn't exist yet (neutral position)
>despite one party being willing and the other not having a stance we have as a society determined that the potential consequences of this and what to do with them are entirely dependant on and are subjects to decision only to the adult despite the child not being able to say "yes", both because they don't have a conciousness and because they lack the ability to make an informed decision
>this is accepted by most societies and you will be called a freak for questioning it
This is where it stopes making sense.

By definition the decision to exist is a FAR bigger one than the decision to have sex at a young age, in fact it's the biggest decision there can be for a human being since all subsequent decision you make are derrived from it. Yet you cannot make such a decision informed (since learning information requires existance) nor can you argue their brain is developed enough (since it doesn't exist). Isn't it therefore hypocritical to allow one but not the other?