You can express your desire to not raise a child all you want, it doesn't change the fact that you made a choice that led to that child being born.

You both have to pay for it because you both made a decision to make it. Both parents have an obligation to provide support, and if one parent wants nothing to do with the kid, that support must be financial. "Why?" Because that kid costs money to raise, and the alternative is the state paying for your decision not to wrap it up. Like hell do I want my taxes paying for your one night stand.

Because you can't make medical decisions for someone else, your one and only opportunity to opt out of being a father is while you're having sex. The only person who gets to decide whether or not to have an abortion is the pregnant party. If they opt not to, but you really, really want them to, then that sucks for you, but refer back to point 2.