It seems, though, that some white supremacists try to use science to confirm their superiority. So they turn to services such as Ancestry.com and 23andMe in order to take DNA tests.
A new study by UCLA sociologists Aaron Panofsky and Joan Donovan suggests that these results sometimes disturb the purists.
The researchers studied 3,070 postings on white nationalist forum Stormfront over a 10-year period. There, some who are shocked that they might have, say, African heritage share their results in an attempt to dispute the findings and confirm their purity.
The researchers say they saw evidence of posters using "the particular relationships made visible by GATs (genetic ancestry testing) to re-imagine the collective boundaries and constitution of white nationalism."
The pain of not being defined as white is so great that they desperate try to redefine what white really is.
Some of those upset with their results then insist that you should take what your grandparents told you more seriously than the science. There are claims that because testing companies are "quite liberal," they deliberately sprinkle in some non-white DNA into results to suit their political beliefs.
Others prefer to believe their mirrors. "I wouldn't worry about it," said one Stormfront poster cited in the study. "When you look in the mirror, do you see a jew? If not, you're good."
And then there are those who just prefer to think of their results as being subject to statistical error.
Do any of these people complain to the testing companies?
A 23andMe spokesman told me diplomatically: "With over 2 million customers, we do get the occasional complaint." He said the company's customer service then tries to help complainers understand how the results came about.
"The average 23andMe customer has DNA from at least five different regions from around the world," he told me.
As for Ancestry.com, its spokesman said he had no knowledge of specific white supremacist complaints. Instead, he said, the largest number of complaints come from people convinced they have some Native American in their blood.
Even though the results given are estimates of ethnicity, the spokesman said: "We are very confident in our science. This is well-established, recognized science that has been published in scientific journals."
Ancestry.com currently traces ethnicity across 26 different regions, as well as 334 genetic communities, which are more granular historical groups of people like "Ulster Irish," "Early Settlers of New York" or "Early Settlers of New Mexico."
"People looking to use our services to prove they are ethnically 'pure' are going to be deeply disappointed. We encourage them to take their business elsewhere," said the Ancestry.com spokesman.
Still, one can imagine the disappointment in discovering you're not who you really think you are.
Perhaps the most tragic postings featured in the research concern those who try to celebrate that they are, as in one case, a mere 61 percent European.
A Stormfront poster replied to one of these optimists: "I've prepared you a drink. It's 61percent pure water. The rest is potassium cyanide. I assume you have no objections to drinking it. (You might need to stir it first since anyone can see at a glance that it isn't pure water.) Cyanide isn't water, and YOU are not White."
I wonder in how many cases white supremacists actually reconsider not only themselves, but the world view they espouse.