The fiercest argument over ST getting banned was probably
this thread here. I'm probably giving a biased recap (I really don't like ST), but I think most of the arguments against it being banned broke down into one of these 4 categories:
1. "It's a fair way to 'balance' 5-color goodstuff decks."I think some players also overestimated how popular 5-color decks are (they're definitely popular, but not anywhere close to the wedge generals or blue combo/ramp generals). Even if there was a glut of 5-color decks running amok, the balance part was still a crummy argument, since the RC remains adamant that format balance is not a concern (this applies for the next two items in this list too).
2. "It's the best way to fight ramp."As above, trying to "balance" a strategy isn't especially relevant, and I've never been convinced that ST was useful for fighting ramp. Instead, it always seemed like one of the better tools for ramp decks to lock down the rest of the table. If you want to play hardcore ramp, the best options are Forest decks (maybe splashing a second color), or artifact mana decks (usually mono-blue, sometimes with a splash like in Oona).
3. "Mono-colored decks need it."This was always a silly argument, since there have always been a few mono-colored decks that do fine without LD, and in the year since ST was banned, mono- decks haven't disappeared. Azami, Arcum, Memnarch, and other mono-blue combo/control commanders are still competitive if that's your thing. There are a variety of mono-black and mono-green decks. Mono-red and mono-white are probably a little underplayed, but that's more because of the limitations of their color (and furthermore, they've got plenty of other mass LD cards without ST).
4. "Players should understand it's anti-social, so it shouldn't be treated any differently than Armageddon or other mana denial cards."Yeah, most players who have a strong grasp of the format are likely to understand how ST can be an antisocial card; unfortunately, many players seemed to fall into traps #1-3, and ended up wrecking games in a misguided attempt to "balance" their group. The problem here is that the format continues to grow briskly, and there's no EDH boot camp to train newbies on commonly accepted standards of play. Remember, this forum reaches a very small audience, and even Sheldon's only hitting a small part of the crowd with his SCG column. So keeping it banned seems like the easiest way to prevent new players from having to reinvent the wheel when they discover the format.
(I dunno about the argument that Primeval Titan getting banned makes Sundering Titan more acceptable. I don't really see how the two cards interact, so you might need to explain it differently.)