to add to the tradition...
Geneses 3:1 Now the serpent was more SUBTIL than any beast of the field which the LORD God had made. And he said unto the woman, Yea, hath God said, Ye shall not eat of every tree of the garden?
Revelation 12:9 "And the great dragon was cast out, that old SERPENT, called the Devil, and Satan, which DECEIVETH THE WHOLE WORLD: he was cast out into the earth, and his angels were cast out with him."
Proverbs 14:12 "There is a way which seemeth right unto a man, but the end thereof [are] the ways of death."
In other words many are deceived because the deceit is subtil or cleverly hidden, such as appearing to be for a good cause.
Just some more thoughts,