Perhaps we don't want the Silents to fall.
I had similar thoughts. Perhaps the Silence are not the enemy, or at least not as evil as we are being setup to believe. The Silent in the White House toilet seemed to be warning Amy, or making sure she told the Doctor something. Yes, it killed that woman, so maybe amoral, but not evil?
"Silence will fall" sounds like a bad thing, so perhaps them not falling is the preferred outcome?