The point of the argue both sides exercise is that it does help get to the ultimate truth. When you are forced to argue for things that you disagree with, you

The point of the argue both sides exercise is that it does help get to the ultimate truth. When you are forced to argue for things that you disagree with, you will quickly come to realize that some of the things that your opponents say are true! That does not mean that their conclusion is ultimately correct, but doing the exercise helps you get out of common mindset that anything said by your opponents is wrong.