No need to think things through - a man was treated unfairly, ultimately by a woman, so the "WAAAAH" machine gets turned on.
More like, so the feminists rejoice and claim that such unfair treatment is ultimately just because the victim is only a man. That's the sexist attitude you, Toni and a few others are exhibiting here.
What a fucking huge load of bullshit.
I've said more than once that the woman behaved badly. We have no idea if the man also cheated or if he also has children outside of the marriage. We know that the wife cheated and the child she bore ultimately was proven not to be her husband's. We don't even know how this information came to be known. We don't know if she, in very good faith, believed the child to be her husband's child or hoped that the child was her husband's or if she knew that leaving her husband for her lover was an impossibility for X reasons and chose to deliberately deceive her husband. We do not know.
What I have said is that the man failed to challenge paternity within the generous 2 year time frame that Finnish law allows and so, by Finnish law, he is legally obligated to act financially as though he were the child's genetic parent and pay support for said child.
The child is more than 2 years old and has already established a child/father relationship with the husband. It is cruel to the child to have the legal father now reject the child because he is justifiably angry with the child's mother and divorced her. I understand the husband's anger and hurt and anguish, even. He has a choice of whether or not to maintain a father/child relationship with the child but Finnish law mandates that he maintain a legal/financial relationship. Personally, I think it is monstrous to reject a child who is proven not to carry your genetic material, particularly when you have already established a relationship with that child and maintained such for over two years.
Now, if the circumstances are different than presented in the article in the OP: The woman abandoned her husband after learning of her pregnancy or soon after and the child never grew up knowing the husband as his father, then the monstrous behavior isn't monstrous and I would go so far as to say that Finnish law is perhaps wrong here. The only uncertainty is that it was more than 2 years before the husband challenged the paternity. Two years is a long time, actually.
At what point can a parent decide to reject a child who is proven to not be their genetically? Before birth: I would agree. The genetic parent reunites with the other genetic parent? Yes. The genetic parent/non-genetic parent raise the child to 2 or 5 or 10 or 17 or whatever age and then the nongenetic parent decides that they've been fooled and reject not only the at fault other parent but the child? That's monstrous. It seems that after a prolonged relationship between false father and child, Finnish law would mandate that the rejecting parent still be responsible for support of the child.
Suppose this: A man has a wife and a mistress on the side. Both women become pregnant around the same time and by a twist of fate, end up in the same hospital delivering at the same time. The husband has told the mistress that he will not leave his wife. She has decided, and he agreed, to place the child for adoption. The wife, meanwhile, has an extremely difficult delivery, delivers by emergency c section and the child is born dead or born with complications and dies a short time later, the wife never having a chance to bond with the child. The husband decides to present his child with his mistress to his wife as the wife's own child and she raises that child to age 2 or whatever age. The truth comes out. The wife...then rejects the child who is not her own? Divorces her husband and refuses to see the child? Refuses to pay support for this child? Also monstrous and also, one would hope, not allowed by Finnish law.