The ban policy with regards to people trying to get back on depends on how they got banned and how they responded after the ban. The vast majority would be allowed back in under a new account with their old one being wiped out. If they want back shortly after they were banned their new account is tagged with double yellows, if it's been a few months the cards aren't required.
That said once you're banned for breaking the rules, we're in no way whatsoever obligated to let anyone back in at all. Once you're proven to be an aggressive/harrassing troll or people in the booth are tired of fucking with it that's enough, as is evidenced with Coleman the Ape, RTR, kage, Sunny Silva, Ramrod, the list goes on and on.
My perspective on the Blue/SEXY BEAST situation is cut and dry and a dead horse. Blue was fighter bashing with double yellows and got banned. Barnett never contacted anyone in the booth. Jeff was pissed over the whole situation and commented on the thread that he would have banned him himself if he'd have gotten there first and taken care of the others on the thread who did the same. Icemanfan got the same treatment as Blue. All admins were in unison on his banning, not just Jeff. Fine, I personally would have let him come back in at that point with a new account and double yellows (though I can't speak for the others). Instead he immediately started account after account yucking it up and stating he couldn't be banned, trolling the board under related and obvious pseudonyms for the better part of a week to prove his case and in doing so he burned all his bridges then and there. We'd had the same problem with him in the ask the fighters forum when he was harrassing Enson even after Jeff erased his shit and told him to knock it off, ultimately resulting in his being blocked from the forum.
SEXY BEAST was double yellow carded for three months for pushing the over-the-line avatars along with BigRon. BigRon rode it out and SEXY BEAST eventually posted a gratuitously worded chunk of "Alice in Wonderland" with his doubles and justifiably got the boot for it. I'm not sure who banned him but it makes no difference to me as I was behind it 100%. He's been gone awhile and though he didn't attack the board after he was banned, he did annoy the hell out of some people including those booth. If he stays I don't personally have a problem with it. If whoever banned him thinks he's burned too many bridges here and wants him rebanned, I don't have any problem with that either. Que sera sera.