This is a horrible idea...
If you want to ban someone, surely you can find a post of theirs that breaks the rules?
If you ban people for being jerks, then we will always be in fear of posting something the mod team doesn't like/agree with. We already have enough of that because the rules are vague and subject to interpretation. If the mods could just say "You are a jerk, I'm going to ban you" it could quickly become a popularity game, and even if it didn't, it would still not be a fair system.
Its not like they are going to just up and decide to ban someone. The subject of such a ban should be able to see it coming.