WT claiming that "viewing child pornography is not considered to be child sexual abuse"?
Depending on the jurisdiction, viewing child pornography is not child sexual abuse. But you will have to show that it is in Australia..
Mathew 5:27,28 says nothing about viewing child pornography being child abuse. (although it is wrong to have sexual feelings towards a child) Children of the same age sometimes have sexual feelings towards each other and male children sometimes have sexual feelings towards a teacher for example.