I'd say that the target shouldn't matter for the bonus, but the intent should. If the caster adds in their Lawbreaker bonus, they're making a declaration that they're intending to kill/enthrall/otherwise do what the Law says they shouldn't. If they want to throw a non-lethal spell, then they can't add in the bonus, and may have to resist a compel to one or another of the aspects their Lawbreaking has twisted. But I do agree that the bonus should work equally well when applied to a target that wouldn't constitute Lawbreaking; once you've murdered a few dozen people, murdering a White Court Vampire shouldn't make much of a change.