I think men should be free of the responsibility for a child they don't want.
In the event of an unplanned pregnancy a man cannot force a woman to get an abortion nor can he force her to carry the pregnancy to term.
Essentially he has no choice even though he is exactly as responsible for the pregnancy as the woman.
So to give men a little more say in the matter, i think that if he doesn't want to keep the baby and the woman does, he should be allowed to forfeit all rights to and responsibility for the child.