Sovereign citizens and other forms of pseudo-law like the German Reichsbürger movement can be seen as a hybrid of fascist disaffection and liberal legalism.
On the one hand they are still firm believers in the state and the law. There are rules, good and fair rules they can trust and that work to their benefit. But on the other hand they can see that something is wrong with society. The good rules they believe in is not followed, instead reality is run by a completely different set of rules, rules that gives them DUI's, rules that demands them to pay child support, rules that repossesses their cars and forecloses their houses. Rules that humiliates them and makes them feel powerless instead of defending their rightful positions as privileged white men.
Facing the reality that the rules doesn't work for you usually leads to cynicism and the belief that the law is corrupt, biased and a tool of oppression. Sovereign citizens on the other hand are too wedded to the idea of the law being just and good and reaches the logical conclusion that if The Law is good and of the power that is imposed upon them is bad, then it must mean that those in power does not follow The Law and that there must be some secret law you can unlock to be treated well.
From there on it just snowballs and they will construct a cushion of nonsense and delusions around themselves to feel good in a world that treats them bad.
The best antidote to this is of course class consciousness. The problem with capitalist society is not that the people running it are breaking the real law. The problem is the uneven distribution of wealth, power, respect and possibilities that leaves the majority hurting so a tiny elite can live in luxury.