We don't have 6 votes for this.
I mean don't get me wrong, after thinking about this rationally for a bit BBM's role would be a ONLY ON CONFIRMED SCUM vig shot which isn't impossible but it still sounds really ridiculous to put a role like this where it could ruin the game based on a player's whims. nth rule of setup crafting is don't assume the player will act the way you expect. It would be a very very bad hosting decision to overlook that.
Even if there's an agreement to autolynch the double hated dude after a misuse, it's a clear in exchange for a lynch and a nk. (I think? I'm not messing this up?) If you DON'T lynch it you play against your wincon because LYLO comes at a blink of an eye.
The argument isn't if it's safe or not to let a role like this live, in fact it probably is, the argument is that this role probably doesn't exist.
Tbh if BBM is scum it wouldn't surprise me if Polly was still scum considering his reaction to the claim. Says he needs a new vote, never ends up rethinking his vote, sticks his vote on BBM anyway because

(Probably because the wagon didn't end up dissolving.)