The original writeup in this node has been deleted, leaving my reply redundant.
An anti-swastika tattoo? Hm... how about a swastika, maybe?
I assume NOFX is speaking out against Hitler, rather than elementary geometric patterns in general. This is a good idea. I'm not sure what symbol would be specifically against the holocaust, but healing might be represented by the Hindu right-handed swastika symbolizing the sun, and new beginnings.
A left-handed swastika in many Asian cultures also represents good fortune. It also represents the Buddha and is one of the 106 symbols appearing on his footprint. This is all pretty directly opposed to the holocaust.
The swastika is one of the most commonly reappearing symbols in human kind, used universally, and for almost anything. Until Hitler came along and ruined it for the West.
In modern times (but before WWII) it has appeared on boy scout logos, American pilots used them on their planes in WWI, and Rudyard Kipling used it for his coat-of-arms. Of course, he called it a flyfot or a gammadion.
But when Americans were given a choice as to what it should represent, they chose hate.