What does unnatural really mean?

In a recent discussion about abortion, the phrase that was repeated over and over by my very sweet friend was "it is just unnatural." My brilliant, but sometimes insensitive husband began to describe very exaggerated things that are "unnatural" just to make a point: cutting your hair, wearing clothes. He's great! This only made my sweet friend a little upset and not at all open to hear the point being made. Plus, sometimes, though on the same side of an issue, Isaac and I tend to be making totally different points, so we don't really help each other.

Anyway, what does natural really mean to us? Is it totally subjective, or is it a phrase that might help to know what should have been, but totally unrelated to what actually is, making it completely unimportant? There are many examples, I believe, about things that seem "unnatural" to me, but that many allow without question. It seems unnatural to me to walk by someone and not say hello, but many people do this. It is unnatural for me not to be more affectionate with my little ones at school, but creepy teachers have made it so non-creepy ones like myself are warned against it. It seems unnatural to know that many children around the world die because $5 would have bought them milk, but I bought the #3 meal at McDonald's instead. Yesterday around two dozen civilians were killed by Taliban militants who seized their bus and killed them all, including children, and beheading some. I heard the news this morning, was truly sad, for a moment. Then I continued my ride to work and had a seemingly normal day in which I didn't think about the event again, until now. Unnatural.