Question

There should be no minimum voting age "..arguable defensible or both

Answer 1

A. It is arguable but not defensible. 

Answer 2

I am not sure what the question is asking. If you are looking for ideas to use to defend both sides then here is a few. (sorry if i misinterpreted the question)
There SHOULD be NO minimum voting age:
-No matter your age, a citizen of the U.S is going to be affected by the outcome of an election.
There SHOULD BE a minimum voting age:
-If you allow children to vote, most likely they will not have their own opinion when voting, and will simply be voting for what a parent, friend, or other peer tells him/her to. We should have a minimum age set to at least an age where the voter can think for themselves and make an educated decision.

Hope this helped.