I used the example of Bernie Sanders since his Jewish tradition has a lot of room for a pro-choice position and it is idle to demand he accept Catholic moral premisses when he is not Catholic.
The same thing applies to secularists. That does not mean no argument can be made. It means–as always–that if you are going to make that argument, you must start where your audience is, not where you are.
Here is Kristine Kruszelnicki giving a sample of what that looks like in “A Secular Case Against Abortion“:
“Is there really such a thing as a pro-life atheist?” asked Marco Rosaire Rossi in the September/October edition of the The Humanist. “What’s next, Intelligent Design Agnostics? How about Secularists for Sharia Law?”
Atheists may not have a pope, but in the eyes of many there is still a proper dogma that all good atheists must adhere to. To be an atheist is to support abortion. Fail to do so and you will be denounced as “secretly religious.” When I joined an agnostic and an atheist from Secular Pro-Life for an information table at the 2012 American Atheist Convention, a popular atheist blogger accused us outright of having “actually lied about being atheist.” [Edit: She also seriously misheard and misconstrued the point of my green banana analogy!]
There is an obvious reluctance to accept that non-religious pro-lifers exist. But we do exist. While we differ somewhat in our approaches and philosophies, our numbers include atheist thinkers like Robert Price, author of “The Case Against the Case for Christ,” civil libertarian writer Nat Hentoff, philosophers Arif Ahmed and Don Marquis, and liberal anti-war activist Mary Meehan, to name a few.
The late atheist author Christopher Hitchens, when asked in a January 2008 debate with Jay Wesley Richards whether he was opposed to abortion and was a member of the pro-life movement, replied:
“I’ve had a lot of quarrels with some of my fellow materialists and secularists on this point, [but] I think that if the concept ‘child’ means anything, the concept ‘unborn child’ can be said to mean something. All the discoveries of embryology [and viability] – which have been very considerable in the last generation or so – appear to confirm that opinion, which I think should be innate in everybody. It’s innate in the Hippocratic Oath, it’s instinct in anyone who’s ever watched a sonogram. So ‘yes’ is my answer to that.”
Secular pro-lifers include seasoned atheists and agnostics, ex-Christians, conservatives, liberals, vegans, gays and lesbians, and even pro-lifers of faith, who understand the strength of secular arguments with secular audiences. The following secular case against abortion is one perspective, and does not represent any single organization.
There’s much more here. Check it out.
It is worth noting (for Christians) that this iron law of argument is rooted in the Incarnation. The entire process of revelation is one long act of God stooping down to our level since we could not come up to his. His final act of coming down to our level meant becoming human (at Bethlehem), poor (in Nazareth) and a corpse (at Calvary) in order come down as low as he possibly could to meet us at every level of human existence. To communicate any aspect of the Word to humans, such humiliation and humility is always required. Even atheists, as here, have to recapitulate it for the simple fact that this is how humans–and especially we fallen humans–have to communicate.