>So, taxation is either extortion, robbery or theft
If ultimate enforcement through violence is the only determinant of whether or not something is a crime, then the very laws that dissuade other crime, say the robbery or theft that you refer to, are themselves blackmail, extortion or some other variation of violent crime.
This circular reasoning does not hold up to scrutiny, which is why it is almost only used in respect of taxation in libertarian circles and nowhere else.
> the very laws that dissuade other crime, say the robbery or theft that you refer to, are themselves blackmail, extortion or some other variation of violent crime
No, because in these cases it's violence enacted in self-defense (often by proxy), and therefore not an aggression.
Defending yourself is not aggression. Going after somebody or their property is.
>No, because in these cases it's violence enacted in self-defense
The use of coercive force is justifiable by the state or it isn't. If you now create justifications for why the use of violence in pursuit of self defense is valid, then you've conceded that the use of violence can be justified.
Which then means the "it's enforced by violence, and all these rationalizations don't matter as you don't have any choice anyway" no longer holds.
There are justifications for the use of violence, therefore we need some ulterior basis other than ultimate enforcement being premised upon the use of state violence in order to explain why 1) taxation is a crime, and further more that 2) that crime morally must be avoided.
You point towards the idea that Taxation is not a transaction you enter voluntarily, but the same can be said of your aggression theory; I didn't consent to any NAP with you, and the NAP is ultimately enforced by violence. I have no desire to abide by the NAP when it doesn't suit me as I never agreed to it.
Ultimately, whether it's the NAP, property rights or taxation, enforcement of pro-social behavior will require some scope, authority or justification which addresses more than just a single individual's consent. "I don't like taxes" is not sufficient an argument to state that you are morally obliged to commit tax evasion.
If ultimate enforcement through violence is the only determinant of whether or not something is a crime, then the very laws that dissuade other crime, say the robbery or theft that you refer to, are themselves blackmail, extortion or some other variation of violent crime.
This circular reasoning does not hold up to scrutiny, which is why it is almost only used in respect of taxation in libertarian circles and nowhere else.