As an agnostic, I don't see why a belief in God is necessary in order to want to live a moral life. I can see the benefits of the Golden Rule regardless of whether you think someone will eternally reward (or punish) you depending on how you behave.
And I have secular friends that I think are perfectly lovely people, so I'm obviously not convinced that without God we are all just awful.
I will say, though, that when people insist religion is the only reason anyone would be pro-life, they sure do reinforce the "atheists have no morality" stereotype.
I'm against abortion because I recognize the fetus as a member of our species and I believe human beings should be valued and protected; at minimum, I think it should be illegal to non-defensively kill someone. I don't consider any of what I just said to be radical, and I don't see why any of what I just said would require religious faith in order to make sense. From the pro-life perspective, when people insist you have to be religious to be pro-life they're insisting that you have to be religious to value humanity and/or think it's wrong to kill others. Great.
But I understand that there's a disconnect here. Many pro-choicers make a distinction between human beings and people, and while the fetus is a human being, they will insist the fetus is not a person. A pro-choicer could believe that all people should be valued and protected while all fetuses can be killed, and there would be no inconsistency in that stance. So, from a pro-choice perspective, the idea that you must be religious to be pro-life is really the idea that you must be religious to believe the fetus is a human being of moral value.
I still think it's kind of sad that some secularists believe you have to be religious to value all members of our species...but I guess it's better than thinking you must be religious to think, you know, killing others is bad.