I think secular people do distinguish between human and animal life, but the reason they do is based on convenience, not logic. Pigs, for example, are happy when you pet them. They squeal when you cause them pain. They eat, sleep, reproduce - all on their own. They are alive in every sense of the word. What makes killing them for food more ok than killing an unborn baby?
Again, I think it comes back to a threshold of convenience that each person has, which is entirely subjective and not based in logic at all. It is OK to kill animals for food because its an efficient way to get calories, and its ok to kill an unborn fetus because that kid may put a crimp in the plans of its parents.
I disagree - while there are immoral and amoral people whose values revolve only around their own convenience, there are many secular people who have a strong moral code and place inherent worth in human life over animal life. You can argue with the logic of that - Where, you might ask, can we derive that worth, or any values at all, if not from a higher power? - but that’s not my point.
My point is not philosophical; it’s practical. I still contend that most people don’t think it’s okay to kill an innocent human being. The challenge of pro-lifers, then, is to show them - in scientific terms that everyone should be able to agree upon - that the fetus IS a human being.
If we put more energy into this approach, it would also be more difficult for libs to dismiss us as religious wackos - which they have done successfully - and don’t tell me you don’t care what they think. We are trying to save lives, and PR matters. If we let ourselves be painted as a bunch of Bible-thumpers, many people will ignore our message, and more babies will be destroyed.