The Michelle thing only came after Apollyon delivered a direct and very personal warning to her and her husband not to mess with them. After that, he gave an order to Namaah to make sure the lesson was as visceral as possible, while still leaving Titus and his son alive. It was horrific and evil, but ultimately, very surgical when you get down to it.
But, ultimately, Apollyon and his fellow Domini have accepted that their existence is monstrous, and that their ultimate purpose is a form of evil the rest of humanity would condemn. Their lot is much like The Operative from Serenity, in that they know the better world they are expected to carve a path for has no place for them. Unlike the Clans, they don't glorify the slaughter they know they'll be asked to commit. One might actually pity them, were it not for the horrors they basically dedicate themselves to as the Jihad unfolds. This was what we wanted to show every time you saw them on scene, at least whenever they weren't wiping people out wholesale.
- Herb
