Many years ago, I made a speech about marbles -- we're all "well-rounded individuals" like marbles.  I warned against prejudice, hatred, jealousy, peer pressure, and the iron curtain marble "can" of communism. 

Another warning could have been from the book of Jude -- evil men have "slipped in among you."  This can happen in our family, our neighborhood, our church, our government, or, in general, our culture.  Jude wrote that they "pervert the grace of our God into a license for immorality and deny Jesus Christ our only Sovereign and Lord." 

What do these "ungodly men" look like?  Are they green, red, blue, or yellow?  Are they striped, swirled, or spotted?  Are they small or large?  We don't know -- that's how they were able to slip in among us.  All we can do is "test" them to see if they are from God (see 1 John 4:1-6), and follow Jesus along the "narrow road" (Matthew 7:13-14).