Why is this playlist copying the wrong songs to my iPhone?
Well, I tried a different tactic. Barring the "Location" criterion, the playlist is basically, "All the 4 and 5 star songs by this set of artists that isn't Christmas music." I have a 4 star smart playlist, a 5 star smart playlist and a Christmas playlist, so I took the time to create a "Headbang Artists" playlist (BTW, 97 artists), and created a new smart playlist that had the criteria of, in "Headbang Artists," not in "Christmas," and in either "4 Star Songs" or "5 Star Songs." This synced successfully.

I'm guessing the other playlist is corrupted somehow and that the duplication of it also duplicates the corruption somehow. But I'll keep it around for a little while in case anyone else knows how to actually fix it in case someone else has a similar problem.