What????? So the sperm donor is at fault here? I just don’t see your reasoning. It’s not as if he had a one night stand with this woman... He sold his sperm to a sperm bank. End of story.
Dude fathered a child and walked away. Father abandoned mother and child. Father did not take responsibility. Intentionally.
Any father who does this should be taken out behind the barn and shot.
This shouldn't be that difficult to grasp.