I think a man should be able to sign away his rights if he was tricked into fatherhood. However take a look at this hypothetical situation. Let's say a couple has been together, and both agree that they want children, so the woman goes and gets pregnant.
Then for whatever reason down the road, the guy decides he doesn't want to be a dad, and decides he wants parental rights terminated. Ultimately it would become a big he said, she said nightmare and both parties would have no real way of proving their side, and it would become a huge legal nightmare and battleground.
So for that reason alone, I'm pretty sure that even if a guy was tricked into becoming a father, the courts are going to make the guy pay child support, and penalize him if he doesn't, unless the mother allows him to terminate his parental rights.