This is actually kind of complicated, and I say that as the mother of a child conceived using donor sperm.
The problem is that no one should be able to sign away someone else’s rights. The right to be supported is the child’s, not the mothers. When a woman doesn’t seek child support payments from her kid’s father because she doesn’t want to deal with him, or is deeply non-confrontational, or is worried people will accuse her of being a gold-digging bitch, and is more worried about that than about her kid, she’s stealing from her kid and giving the money to the other parent. I am willing to believe that there are times when it is legitimately in the kids’ best interest not to pursue support, but I think it would behoove more custodial parents to be aware that the support belongs to their kids, not them.
On the other hand, donating sperm does not make someone a father. Exactly what does make someone a father is a lot more complicated than that, and it’s not really well defined: it’s not the sex act, because lots of babies are conceived without sex. It’s not being married, because lots of parents aren’t married. It’s not the genetics, because lots of men are legal fathers (and moms are legal mothers) to kids that they don’t share DNA with.
I mean, if she had gotten pregnant by him through regular but non-affectionate sex, and they had the same agreement, would this ruling still seem unjust? If so, why does the method of conception matter?
If, on the other hand, they were a boyfriend/girlfriend and had normal sex, got pregnant, he freaked out, she thought she didn’t need his money/want his involvement, would you be ok with her signing away her daughter’s claim for support? Why does the mood of the sex matter?
If a happy couple intentionally used IUI to get pregnant using the man’s sperm, but then broke up before the baby was born, should that man be able to get out of supporting his kid because he was just a donor?
What if a happy couple conceived a child using a sperm donor, but broke up before the baby was born. Should that man be liable for support?
So it’s really confusing about what, exactly, makes a man a father. I don’t have too much sympathy for this couple because due to all this confusion, we have a whole complex set of institutional apparatus established to make it clear that whatever actually makes a father, sperm donation is not enough. Why anyone would ever circumvent that apparatus is beyond me: it’s literally like $300 to have sperm washed and and IUI performed, if you aren’t doing anything else. Having a lawyer draft whatever agreement they had must have cost more.
What we really need is a system that recognizes both women as legal parents to the child so that the state can compel support from the other mom. That’s the reality here.