There were abortions in Christ's time. There have ALWAYS been abortions as much as there have been hookers. They are terminating THEIR pregnancy for whatever THEY choose because YOU refuse to take in all the unwanted babies in the world. So, in a round about way, YOUR refusal to raise all the children in orphanages or foster homes is what is upping abortion. 
There has always been infanticide, so we should allow it now.
Step-parents have always found ways to murder step-children, and it's a natural thing because we see it happen with all kinds of animals, so we should allow it.
People have always killed animals in whatever way worked, regardless of their pain and suffering. And that is natural, we see it in all sort of animal interactions, so we should drop all those silly laws about how cattle and pigs can be killed, and the ones about cruelty to other animals, too. Why, I've even see footage of animals eating an animal that was still alive and screaming in pain, so it's natural!
People have always fought over land, and the losing group was driven away, killed or kept as slaves. We see the same thing happen in animal groups, larger herds will take the better land, single animals are usually driven away, so it's natural and normal and should be allowed today.
Many, many "civilizations" sacrificed their children, the children of their enemies, the children of their slaves, their slaves and their enemies to appease gods. It's always happened, so we should still allow it today.
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Of course, in opposition to your moronic argument, there are the facts that humans are called to rise above animal nature and to follow the real God.
Oh, and by the way, Christians do run orphanages, adoption agencies, and schools all over the world. We'd still run them here if it didn't offend so many Atheists who think it's against the First Amendment. Christians also adopt more children and foster more children that liberals and atheists (and do so even when NOT murdering their own kids.) Christians also help other Christians to adopt, raising money to meet the incredible expenses...one of those results of the government sponsored slaughter of unborn AND the government red tape involved in adoption.
