I take the point to be that if the judge doesn't uphold the DMCA safe harbors, they need to tell Youtube what they can legally do. Viacom's stated alternative

I take the point to be that if the judge doesn't uphold the DMCA safe harbors, they need to tell Youtube what they can legally do. Viacom's stated alternative is for Youtube to divine the intent of the copyright holder. Arguing that the alternative to DMCA is absurdity and divining the intent of Viacom would have been impossible will tend to undercut this alternative.