That is the opinion that struck down poll taxes.
You have a right to vote, so levying a tax upon the act of voting is not permissible. Obviously, if it is a right, it means that even someone with zero money should be able to do it, and you can't pay a tax if you have zero money. The tax prevents poor people from fully exercising their rights.
As such, taxes that appear to be on the exercise of a right are usually worded such that they are actually excises on a legal privilege that is suspiciously similar, or upon an accessory privilege, without which the exercise of the right is largely pointless.
You can build as many steel mills as you want on your own property. But doing so is pointless if you cannot transport the steel over public roads or sell it to customers in the public marketplace, unless you have a great need for vast quantities of steel on your own property. There are quite a lot of foil-hat-wearers out there that try to tease out the line of separation between taxable privileges and untaxable rights, but the reality is that none of their opinions hold any sway unless they have millions of dollars to spend on lawyers and lobbyists, or millions of supporters to march on the capital. As such, a lot of "Sovereign Citizen" propaganda revolves around the insane idea that a state with near unlimited power may be compelled to obey its own laws, even when doing so would be contrary to its own interests.
This is the same phenomenon that results in your tabletop RPG's resident rules lawyer getting their characters killed off. For any obscure rule they can argue to their own advantage, the GM can always just roll behind a screen and say, "Oh dear, the goblin scored a critical hit. What an unlucky occurrence. Your character dies. Again."
For instance, the Supreme Court has also ruled that it is permissible to prevent someone from growing a crop on their own property, never to be exported off of that property, because that satisfies some demand that would otherwise impact prices in interstate commerce. Essentially, the state said it can prevent you from growing corn in your garden, because that means you won't buy as much corn--which could be imported from another state--at the grocery store. In order for that ruling to be consistent with the poll tax opinion, the US cannot recognize that engaging in commerce and providing for your own livelihood is a natural right. Because that would mean it couldn't be taxed, and the government needs those taxes more than you need to buy your own food and shelter.
Anyway, the point I'm trying to make is that many of the things you may call "legal right" are probably just legal privileges, and that if something is taxed, the government does not recognize that you have a right to have it or do it. This is disturbing to some people, because it provides a practical test to unequivocally show that they have far fewer rights recognized by law than they believe themselves to have.