So it seems that before I managed to post my clarification, NetiquamErro and LU correctly (and may I say it, more eloquently) pointed out the flaws with “arguing the other side”. Although I agree (see above), I think that NE is incorrect.
Furthermore, even were that not the case, it is virtually impossible to be truly convincing when simply pretending to believe as you do. It’s one thing to defend a position that matters to you. Your brain is fully employed in trying to find the gaps in the oppositions defenses and the inherent truth and logic in your own. But when your only aim is to argue against yourself, you’re simply not going to do a good job, no matter how hard you try. The lack of emotional investment means that your bound to be destroyed in a reasonable discussion by anybody that actually believes in what they’re saying, even an intellectual inferior.
Although from a moral standpoint you were correct, I must disagree with this point of yours. I can tell you with confidence that I have done the very thing you have proclaimed impossible, and have successfully persuaded opponents against arguments they were very emotionally attached to, although I fully supported their position the whole way along. In fact, I was successful enough that when I told them I was actually “on their team”, I had to re-argue their position while they took up my points, and I had to refute them one by one. And I wasn’t arguing with an idiot either.
What you say about emotional investment – if you enjoy the challenge enough, you can be emotionally invested in the argument you don’t believe, albeit a superficial attachment.
One place where I used this tactic (perhaps where i developed this tactic) constructively and not just for entertainment is in the Beis Hamedrash. When discussing a sugya, people often have preconceived notions and unjustified assumptions (generally called הנחות) or sometimes have come out with a “mehalech”, and although they may be correct in their assumptions/mehalech, they may have the wrong reasons to prove it. There is a big toieles to play the “devils advocate”, להגדיל תורה ולהאדירה. In this case, ביקוש האמת obligates you to try get out of any unnecessary assumptions which you may have picked up along the route without legitimate reason. When a chavrusa of mine will say something, I will automatically (subconciously) take on the opposite position, not in a offensive fashion but in a defensive fashion. This is not being מגלה פנים בתורה שלא כהלכה, this is לימוד התורה.