But, he can only be persuaded by the arguments that will necessarily persuade him, not necessarily those which correspond to reality. What merit is it to simply find the right button to push?
Compare with adventure games that more or less consists of finding the right buttons to push in some order :)
Also note that "merit" and "enjoyment" are different things.
As for merit vs. enjoyment, I believe that the best merit of discussions is the enjoyment one can derive from it.