play devil's advocate take a side in an argument that is the opposite of what you really want or think.
☞ A translation of the Latin phrase advocatus diaboli, devil's advocate is the popular name for the official in the Roman Catholic Church who puts the case against a candidate for canonization or beatification; he is more properly known as promotor fidei 'promoter of the faith'.
2011The Charade Goes On Since my earliest days to today, I'm cynical but a dreamer with an idealistic streak. I love a good argument, to play devil's advocate, to see both sides of the coin almost endlessly.