I'm sure you and Brim will have a much more intellectual repertoire than I could provide, so I'll just say this then back off for a bit.
I've read back a bit, and as I see it, a member was banned for being an ass. Presumably, they came back under a new identity. Their new persona, while not being ideal towards the main objective of the forum, still managed to not be as vitriolic, and while they didn't contribute much to serious discussions, did refrain from being a total ass, and possibly managed to try and make the forum a more active place.
I'd say the initial ban worked, and there is always the option to impose another ban if said person returns to their previous ways. But as long as they're going by the rules of the playground now, what's the harm in letting them play?