Well, if you acknowledge the fact that the "natural" situation is different, then why can't you accept the fact that the "legal" situation could or should be different as well?

And, why should the existence of the right of a born child to be supported by both of his or her parents depend on someone's choice concerning abortion?

In my opinion, you are proposing a meaningless argument since children have the right to be supported by both of their parents REGARDLESS of the legal status of abortion and any of the issues that that status includes. In short, even IF a man has a say over the outcome of a pregnancy, the man would still be legally bound to support that child since that child has the right to be supported by both of his or her parents AND since it is in the interest of the state to protect that child's rights. Of course, either one of that child's two parents can personally choose to provide that child with all the support he or she needs...as long as the state directly or indirectly agrees with that implied or agreed-upon mutual agreement. But, I would argue that it isn't in the state's interest if they where to accept a system whereby a man doesn't have to provide support for a child simply because he wanted a women to have an abortion since that choice has nothing to do with the woman's ability to support the child. The child's rights are, in effect, INALIENABLE, at least in the eyes of the state. Thus, a child's right to be supported by both of his or her parents cannot simply be taken away from him or her pending the outcome of the man's decision concerning a woman's potential abortion. Hence, your argument that a man should not have to support a born child if he wishes that the woman get an abortion, yet she doesn't, is meaningless.