The white lies we tell each other to make society work are coming out one at a time. That's why france disallows paternity tests. Then again is society ready to move beyond the nuclear family? i dont think so
I differ with the previous poster in that I don't think that many men are unknowingly raising children that are not theirs. I've seen estimates that vary between .6% and 5%.
I do think that a man ought to have the right to know if he's the biological father and I think it's understandable if he wants to leave if he isn't. Yes, familial bonds are important but what kind of family do you have if the lies run that deep?
Yes, but I've always assume reasonable people want to know this because it would prove infidelity by their spouse, not because they specifically care that their child shares their genes.
I don't think that most people distinguish between a child from their own genes with an adopted child, unless there's some falsehood in play. At least I hope not.