People are reading way to much into this scene. Vergil only did it to piss Mundus off and for no other reason not to mention the child that was killed was this worlds equivalent of the anti christ. People should be more offended that Vergil used a gun.
When coincidence is so convenient, I prefer to call it fate.
What makes the scene disgusting isn't Vorgel just killing the fetus and Lilith. It's him shooting her, pausing while giving a **** eating grin to let her realize he just killed her fetus aberration and then shooting her in the head for no reason. The moment he killed the fetus she was useless to either him or Mundus. He killed her just to be an even bigger dick.
Frank Zappa is God. Fact. King of Heroes, do you have enough swords?!