David Lloyd

It does not do to rely on silent majorities, Evey, for silence is a fragile thing... one loud noise, and it's gone.

But the people are so cowed and disorganised. A few might take the opportunity to protest, but it'll just be a voice crying in the wilderness.

Noise is relative to the silence preceding it. The more absolute the hush, the more shocking the thunderclap.
Ours masters have not heard the people's voice for generations, Evey... and it is much much louder than they care to remember.