Unless your opponent has proven to be inferior and stupid time and again, it is reasonable to assume that their proposal has some merits. This may turn out to be false, in which case it ends at DH6 or DH7, but, more often than not, a disagreement between two smart and people can be traced to their priors (e.g. Talmud is the ultimate source of wisdom vs Experimental evidence is the final judge), and those are worth arguing over, not the specific argument, which tends to be many levels removed.