Do you believe in the higher value of humans over non-human animals? If so, you are borrowing some of your morality from Theistic philosophy. Evolution provides no foundation for this higher value. The philosophy that has its foundation in evolution equates man with animals. In this view, man does not deserve a higher value than animals. This morality is based on one’s ability to suffer.
Is it more moral to kill a pig that can feel pain or a fetus that can’t feel pain? Atheists would save the pig. Is it less moral to eat bacon, seeing as how the pig can suffer and humans killed it, or practice cannibalism as long as the human died accidentally and the relatives say it’s OK? Atheists would enjoy a good batch of John Smith stew. Is it more moral to kill a deformed or mentally retarded infant so they won’t have to suffer all of their lives, or let them live (although this “suffering” is debatable)? Atheists choose to end the suffering. Some atheists would still let the child and the fetus live and also eat bacon, but if they do they betray the fact that their philosophy does not totally align itself with atheistic philosophy. They borrow from Theistic philosophy.
Would you be more disgusted at a picture of a dead fetus? Your answer will tell you what philosophy you live by.