"The alternative I suggest to a radical youth liberation argument is not youth enslavement or unlimited state power. It is one where liberty is the assumption (especially in cases where parents and children agree), and we carve out specific exceptions to reflect our most basic moral values as a society."

Sorry, but everything you say after "liberty is the assumption" precludes the possibility of liberty being the assumption.

Liberty stems from agency. The moral patient has no agency and hence, no liberty.

Unless of course your notion of "liberty" involves only the freedoms to not exercise choice. Something you seem to be very fond of when it comes to youth-rights.

Dissident knows that the latter isn't freedom, and astrologer knows that the former isn't liberty.

You might want to bone-up on the legal and moral concepts you tout in your arguments. They predate your idiosyncratic usage, and familiarity might breed a different appreciation of them.

Dante