The decision reached the right outcome (overall, the use was not fair) for really the wrong reason. What the decision probably should have done was to rule that what Andy Warhol did
was transformative, and therefore the first factor favors fair use,
but wasn't transformative enough to be overall fair use, as the other factors (in particular, the fourth factor) weighed against fair use far more strongly than the first factor weighed in favor.
However, the court essentially boxed itself into weighing in only one the meaning of factor one, so it tries to reach the decision by half-importing factor four (the degree to which it substitutes the original) into factor one analysis. Furthermore, it ties itself into a knot to argue why Andy Warhol's use in the original prints was transformative and overall fair use, but the use in the newspaper article wasn't transformative.
The dissent manages to be even worse by, as you point out, essentially arguing that everything Andy Warhol does deserves to be fair use because it's Andy Warhol. Oh, and taking as many potshots at the majority opinion as is possible. As bad as the majority opinion was, the dissent is even worse.