One of my all-time favourite illustrations:
Bible Teach, chap. 16 p. 154 pars. 1,2, & 12 Take Your Stand for True Worship
1 Suppose you found out that your whole neighborhood has been contaminated. Someone has secretly been dumping poisonous waste in the area, and now the situation is life threatening. What would you do? No doubt, you would move away if you could. But after doing that, you would still face this serious question, ‘Have I been poisoned?’
2 A similar situation arises with regard to false religion. The Bible teaches that such worship is contaminated with unclean teachings........
12 Suppose you saw a piece of candy lying in the gutter. Would you pick up that candy and eat it? Of course not! That candy is unclean......To take a stand for true worship, we need to have a viewpoint like that of the prophet Isaiah, who told true worshippers: “Touch nothing unclean!”—Isaiah 52:11.
I will gladly provide any lurkers with various pieces of literature based "unclean candy" via PM if they wish to see if they have been "poisoned".