Yeah, I loved my freedom loving CN barbarian that didn't give a flying **** what anyone else thought. He was fiercely loyal to his friends and allies and was honest to a fault because he decided that for him lying was a sign of weakness. On the other hand if I go into my way back machine [queue wavy graphics] I had a player that decided his CN would help the thieves they were hired to find escape out a window. He was surprised when the rest of the group objected and one of the thieves took a swing at him since other members of the party had already made attacks. This was the first combat of the campaign.
I blame the 2E(?) description of CN as being basically loony tunes character that would change sides in the middle of the fight "just to see what happens". You know what happens? Best case? You're no longer trusted by the other party members and are no longer allowed to tag along. Worst case? The other PCs decide you're now an enemy and take you out as well. In either case, write up a new PC.
Want to play The Joker and just want to watch the world burn? You aren't CN, you're CE so find another game. Want to play a person that is willing to work with the group but values personal freedom. Someone that is still aware of the world around them and understand that there are consequences to your actions and that the group can kick you out at any time? Welcome to the club.
I ban evil PCs because I just don't want to deal with it. If you're LE but never actually do anything truly evil, why bother putting that on your character sheet? Last, but not least, I don't really care about alignment of my PCs in general. Alignment is just a handy shortcut for describing a cluster of motivations.