Surprisingly there isn't a coin dedicated to extremist values like a nazicoin so I guess they are using bitcoin and a mixer or something like Monero instead. Most use fiat anyways
Extremist values have no reason to exist outside of the scope of another coin, and even with this in mind, there have been some actual nazi projects started as a joke - or as a provocation to see whether decentralization is real, or if censorship is indeed possible. The crypto community generally does a good job at rendering them irrelevant, although sometimes at the expense of censorship, which proved the troll's point.