Doug, based on my observations of someone I know, I am afraid it is mostly the "shock value." The guy in question if full of resentment for the alleged rejection of his "intellectual talents" by the academic establishment - he dropped out of a grad school and ostensibly became a truck driver. His use of Nazi symbolism serves him two goals:
1. it has the guaranteed effect of pissing off the group he loathes (academicians and mainstream intellectuals) and;
2. it puts him in control of a conversation in a way no other subject could; being a truck driver, he cannot control the coversation in the way a respected intellectual can, but when he starts throwing Nazi slurs he becomes an immediate center of attention during and after the conversation.
It is pathetic, like a child wetting himself to get the attention or spite his parents, but it works.
But as Jim h. correctly said, the guy is too individualistic and unconventional to be accepted by any self-respecting Nazi.
Wojtek