Behold,I send you forth as sheep in the midst of wolves: be ye therefore wise as serpents, and harmless as doves.

-Bible (NewTestament)
St Matthew10:16.

A book is not harmless merely because no one is consciously offended by it.

-Eliot,T(homas) S(tearns)
  Religion and Literature.

A man's behaviour may be quite harmless and even beneficial, when he ismorally behaving like a scoundrel. And he may do great harm when he is morally acting on the highest principles.

-Shaw, George Bernard
  BB.The Doctor's Dilemma, act 3.