Unfortunately, not everything can be unabiguified (not a word, but I'm using it anyway) to the point of having a black and white rule for it. Some things must be taken on a case-to-case basis. Currently, any player names with swear words in them are banned immediately, and any other players (such as nazibird) are discussed on a case-to-case basis.
I know we have a no-swastika rule on the server, but that's mainly because Minecraft was so permeated with people who wanted to make them all over the place. People thought swastikas were "cool", and in my mind, that's a bit wrong. There was nothing cool about the Nazi regime or what they stood for.
A name that someone cannot change, we're a bit less strict on, because they cannot change it. Because of this, I will not be banning nazibird or telling him he cannot play on our server. If anyone has a major problem (and is actually serious about it) with the name, then please PM me with details on why exactly you have a major problem with it.