Personally, speaking solely as a human, I think abortion should be retroactive to the age of 18!
Seriously, that was a joke, altho I would imagine there are a few parents of unruly children who might agree with it
But getting back to the issue as defined, yes the man was 50% responsible for creating the child. So if a woman has an abortion, perhaps the man should be castrated at the same time.
There are plenty of people looking to adopt. Abortion, no matter who took part in the creation of the child, should be abandoned for adoption instead.