It's a debate I've seen had. The winning argument seemed to be that the father was complicit and knew the risks (even with contraception). There's also an issue that no person can demand another person undertake a medical procedure.
However, we should have sympathy for people who are lied to and tricked into becoming fathers (it does happen) and then have to be financially responsible for decades through very little fault of their own.
Maybe there needs to be a sliding scale where people pay different amounts and if someone is lied to (and it can be proven), they shouldn't be as liable. Although you know this will just result in people pretending they've been lied to.
