The devil can cite Scripture for his purpose

Meaning: 1) Bad people can appear to be good to achieve their objective. 2) Even good things can be twisted to achieve bad ends.

Note: devil (noun) = (in Jewish and Christian belief, usually "the Devil") the chief evil spirit or Satan; an evil or cruel person; a trouble-maker or self-willed person | cite (verb) = quote (words from a book etc) to support an argument | Scripture (noun - also scripture or Scriptures) = the Bible; the holy writings of a religion | purpose (noun) = requirements; objective

Origin: Spoken by Antonio in "The Merchant of Venice", written by William Shakespeare (1564-1616):

Mark you this, Bassanio,
The devil can cite Scripture for his purpose.
An evil soul producing holy witness
Is like a villain with a smiling cheek,
A goodly apple rotten at the heart:
O, what a goodly outside falsehood hath!