Fighting Tur is going to be cheaper than fighting Viacom. He doesn't have Viacom's deep pockets.
But Tur does bring up an interesting point.
Does Google/YouTube have a way to limit or block infringing content?
The answer is maybe.
Sure they can tag a file when its uploaded, such that any attempts to reload the same clip will cause it to be rejected. And they can ban a person from uploading content if they are found to be uploading copyright infringing material.
Yet, they can't stop someone from taking a "clean" copy and uploading it, or manually removing their "digital watermark".
The point is that they could have made a reasonable effort to try and stop abuses. Even if its not 100% effective, it would have shown that they were trying to comply with the law, rather than ignore it.
IMHO Tur and Viacom's cases do have merit.