Playing the Devil’s Advocate, in the overwhelming majority of situations, is an intellectual fallacy.
The goal of playing the Devil’s Advocate is to get someone to consider the logic found in a position they disagree with. However, in any instance where this is necessary, it means that the person being spoken to has narrowed the field of positions to 2: (A) “The position I agree with” and (B) “the position I disagree with”
In an A-B only situation, there are 4 possible positions:
1) Agreeing with Position A
2) Agreeing with Position B
3) Lacking an opinion due to lack of concern or lacking the necessary information to form an opinion.
4) Refusing to have an opinion.
If you refuse to have an opinion on a topic, you have no rational right to push someone to consider that their opinion may be wrong. You abstain, courteously, and therefore forfeit judging or influencing the opinions of others.
If you lack an opinion due to lack of concern, why do you care enough to make someone else consider that they might be wrong?
If you lack an opinion due to lack of information, how do you suppose yourself capable of properly questioning someone’s rationale for their opinion?
If you agree with position A and are arguing position A, you are arguing for the position you agree with, and as such are not playing the Devil’s Advocate; you’re simply arguing your own opinion and claiming to play the Devil’s Advocate to be a dick.
If you agree with Position A and are arguing Position B, in an attempt to play the Devil’s Advocate, all but the most mentally astute will degenerate any logic that may exist within Position B down to stupefied verbal diarrhea and insist that it is entirely logical because that is what they perceive Position B supporters to do. Afterall, you have already determined that position B possesses inferior logical merit, or else you would not have chosen to personally agree with position A to begin with.
If someone tells you they’re “just playing Devil’s Advocate”, exit the conversation immediately. All they’re really doing is stroking their own ego or trying to make themselves look morally or intellectually superior.