Oh I don't like the argument at all. I felt disgusted even writing it. I also don't like the argument of using self-defense as a reason to shoot people or the death penalty or frankly the assumption that other people have evil intent. I think the vast majority of us are trying our best and accidentally hurt people (EDIT: and that people feel hurt after our actions, not necessarily caused by them but more likely correlated).

But I do believe that some people who are pregnant and would like abortions may perceive the child as being parasitic (not a parasite, as I also don't like to attach strict labels of badness to one's identity but to focus on behaviors).

So I agree it sounds crass and yet think if others want to use self-defense for other arguments defending their harm to others, I don't see why that same argument couldn't apply here.