Furthermore, the law needs to applied equally, there are cases of child support judgments against men who were not the biological fathers of the children they raised, but yet they were accepted as the father of the children. Similarly, what do you do in the case of a sperm-donor operating through a sperm-bank whose sperm sires a child, he is the biological father, should he be financially responsible for his child?
The sperm donor should absolutely be held accountable for his biological children.
I think most states, including AZ have laws that allow a father to dispute and gather dna evidence to dispute fatherhood of a child. They have to prove it AND walk away from the child. And they have to do it in a certain time frame.
No different than if a man marries a woman with children, he becomes responsible for them. Or as my lawyer told me, "I didn't marry her. You did!"