I don't think you actually understand the argument. Fairness is on the side of the man getting rid of responsibility. If you don't like that then it's fine, but stop the bullshit please.
Edit: Ultimately i don't really care even if it were not fair. I would still put a currently productive member of society above a mere possibility.
At that point it's not the fetus right, that's just after the child is born, it's the woman's, it's not that hard to get, really.
If we consider unprotected sex in these conditions a mistake, then the woman would be the only one to pay the price for it in your scenario no matter her choice regarding an abortion because she still would have to subject herself to a medical procedure and would have to shoulder all the issues related to that or have to pay for the child by herself. The man, on the other hand, would just walk away with no trouble associated to his actions.
Hell, in that situation, if we discount the risk for infections, for a man unprotected sex without wanting a child wouldn't even be a mistake because he'd have no risk associated with it, he could just waltz out of the door.
You are trying very hard to say that fairness in amount of choices is the important part, but in reality it is the fairness in the face of consequences that matters, whoever shoulders more risks, obviously gets more room to decide and the freedom of choice of each individual cuts off at different points.
What you are advocating is not fairness, it's a man's right to do what he wants without having to consider the results of his actions.