How can it cruel and unjust?
By breaking her word she generated a financial loss on another person.
This loss has to be restituted. It would be cruel and unjust to not do so.
Plus, how would this affect the child?
1) Turning word of mouth into something that has legal consequences has a large potential to turn into an exploitable, broken law. Think of how many men would try to get away with not paying child support by claiming that they were "promised" something they never were.
2) There is no reason to take it that far and burden a single parent with child support payments in addition to the already difficult job of raising the child, all so that the father could get away with having sex with whoever he wants — after taking "promises" from women that they aren't going to keep any babies resulting from his sperm, of course.
3) It would affect the child because he/she would be raised a single parent who, thanks to such a law, would most likely have to work long hours to make ends meet. Instead of the single parent's undivided attention being directed toward raising the child, she now has to divide it between that and working as hard as she can to secure a living for her and her child (the latter being her child
and the man's child, the man who was "promised" not to have to take responsibility for any resultant children after sex).
It is pathetic to let women abandon their responsibilities.
They don't, though: they still have to raise the child/children, so I don't see where this "abandon their responsibilities" thing comes from.
It doesn't matter for this topic. The point is that they should be.
As I stated above, I don't think there's any way for them to be legally binding without huge potential for exploitation. It would be a deficient law at best and a cruel one at worst (that's not to say it can't be or isn't both, though).
But that is simply the result of her choice.
In an analogy, imagine i lend you my cellphone, and you put it in a bag with yours. You slam the bag against a wall several times and both cellphones get broken/destroyed. We both went through a loss, but both were caused by you. Therefore, you still must restitute what i lost.
How about this: Imagine I lend you my cellphone, and you put it in a bag with yours. I know that both cellphones have a chance of being broken for whatever reason inside the bag, yet I say, "I don't want any broken cellphones, okay? I'm not going to pay for any losses in case my cellphone is broken." Both cellphones get broken, but I demand that only you pay for both to be repaired/replaced.
How does that sound? Because that's how I see blaming
only the woman in this scenario for the pregnancy and wanting her to make all the child support payments, to be honest.