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!"
“No different than if a man marries a woman with children, he becomes responsible for them.”
Rape is no different?