I am concerned for the security of our great Nation; not so much because of any threat from without, but because of the insidious forces working from within.
— Douglas MacArthur

Loss of freedom seldom happens overnight. Oppression doesn't stand on the doorstep with toothbrush moustache and swastika armband -- it creeps up insidiously... step by step, and all of a sudden the unfortunate citizen realizes that it is gone.
Baron Lane insidious quote

That's the thing about depression: A human being can survive almost anything, as long as she sees the end in sight. But depression is so insidious, and it compounds daily, that it's impossible to ever see the end.
— Elizabeth Wurtzel

Partial truths or half-truths are often more insidious than total falsehoods.
— Samuel P. Huntington

In recompense, envy may be the subtlest - perhaps I should say the most insidious - of the seven deadly sins.
— Joseph Epstein