From Laozi's Daodejing (69):
There is no mistake greater than making light of an enemy. By making light of an enemy we lose our treasure.
I would translate this thus:
There is no greater disaster than underestimating the enemy. By underestimating the enemy, we end up losing our treasure (or what we treasure?).
And I'd say that our treasure, and what we treasure, are our constitutional rights and freedoms.