It means "outlaw" in the old sense of "our laws do not apply to you," including laws like "don't kill this person." It has additional meanings of "decent folk should kill this person on sight, so they stop using up our good air."

It doesn't mean "vile person." It means "the entities that vile persons can feel good about despising, because they're at least human, and these aren't. And not like bugs or trees aren't human... like cesspits aren't human; like diseases aren't human."

I posted about it at InsaneJournal.