i am a pro choice guy. its her body, whatever she wants to do with it then thats her decision, nobody elses.
but i do agree, if i knock a girl up and i never make any attempt to support that child, then i dont see how i should be reliable for it. thats part of pro choice in my eyes- since she made the decision she has to live with it. if she wants the guy to support the kid, then she should stay with that guy or at very least allow him to have half custody.
where child support comes in is if the kid is born and the dad does start supporting it, then he must continue to support it until the child is 18. you cant have it both ways, you cant just say "meh, i dont care anymore". that would be completely unfair to the mother.
but i myself have been with girls who did everything they could to get knocked up by me. lying about pills, trying to fuck with condoms... so if i make it clear i dont want a child and there is no evidence that i ever even tried to support it, then it should be up to the mother to support that child solely. because in the end, it was the mothers decision to have sex too.