Where's the blind rage come from?

I was just looking for some interesting abortion-related discussions at Delphi Forums, when I stumbled into this. (WARNING: VERY crude and nasty language)

What's with these people? Where does the blind, impotent rage come from?

The only underlying thing I can pick out is the idea that their sense of self is so constricted that there's simply no room for anything else. It's like, "If the fetus exists at all, then I AM NOT REAL!" And they have to deny the very existence of the fetus in order to assert their own existence. It's really creepy and sad.