QFT!I think that the majority of DMs ban Evil characters not because the game is "Default Good". I think the majority ban evil characters because players use "I'm Eeeevil!" as an excuse to be an ass at the table.
Just like many DMs don't like Chaotic Neutral for that very reason.
The main culprit is the use of alignment as an excuse for party backstabbing and plot derailment.
And that's not limited to CN/EVil. Everyone here, I'm sure, has ran into one guy who plays Lawful Stupid, much to the detriment of everyone else at the table.
And that's why D&D would be better off if there were no alignments at all. Really, why didn't they just get rid of them in 4E?