The Catholic position against abortion is based on the view that abortion is the killing of a defenseless person, and that the fetus is a potential person.  The view that killing a person is wrong isn't restricted to Catholicism or any other religion.   Rather, it's a fundamental principle of secular law, even in highly secular nations.   And the view that abortion is wrong isn't confined only to religious believers.

If one wants to argue that the fetus isn't a person and the government should fund 10,000 abortion clinics, he has the free speech right to make that argument.   But by the same token, those who DO believe the fetus is a person ALSO have the right to their say on this matter.    Right?   Or are you arguing that only atheists or those with your specific views on human reproduction have free speech and political rights in the U.S. as regards abortion?