Good question. If they lived with the mother in the same house (unfortunately, a lot of these "fathers" disappear and are no where to be seen -- esp. in the "inner cities")and were a participant or an enabler to these atrocities, then I would say yes. I don't see how they could live in the same house, condone it, and be exempt from guilt.
That's what got me so mad about the Joel Steinberg/Hedda Nussbaum case so many years ago (he had beat his little girl Lisa to death, and the severe beatings were going on for some time.) I always thought Nussbaum should have received a jail sentence as well as Steinberg for not trying to stop it, or report it. And she was a NYC career woman yet...so she had the financial independence to leave him if she wanted, unlike a lot of battered women.
unfortunately, not every abandoning father is from the "inner city". joel steinberg was a rich attorney. this girl apparently was at least middle class- how likely is it that the baby's father was lower class? nah, he's probably every bit as middle class as she is.
here's a more general question: should unwed fathers be held accountable for the children they help procreate?
lady susan