> By an argument with exactly the same structure, every State is totally illegitimate.
I'd be fine with that. A state can confer value to some extent and still be illegitimate and immoral.
> To be consistent, you would have to argue that taxation is equivalent to armed robbery,
No, because taxation do not require the use of arrest as an enforcement mechanism. I am perfectly happy to consider the use of prison for failing to pay tax to be abusive.
I would, one the other hand, also consider it perfectly reasonable to place restrictions on most societal benefits from someone failing to abide by tax law, and to resist someones attempts to make use of them. Including denying them access to shared resources such as public roads.
If someone is able and willing to put themselves entirely outside of society, on the other hand, and so don't want to pay taxes as a result, I'd support that.
> law enforcement arresting someone is equivalent to kidnapping, and so on.
I do believe all countries massively overuse arrest and incarceration, yes.
I would tend to find it immoral except where failure to do so puts innocent people at substantially higher risk. Even then I believe we have a strong moral duty to seek the least invasive intervention, which would e.g. imply that if/when we are forced to use prisons they should restrict peoples freedoms as little as possible.
Even more so because the evidence is that strict prison systems produces more reclivism than more lenient system. As such, a lot of our "justice" systems not only harm those imprisoned but also inflicts further harm on society by doing a poor job at reducing reoffending, despite the fact that we know better methods.
We will not avoid inconsistencies, but we can seek to minimise them to only those circumstances where we have no other recourse. We have a recourse other than murder. For starters, we have prison. Most murderers that are released from prison never kill again, so the risk is minimal. Arguably low enough that capital punishment quite possibly kills more innocents than releasing murderers from prison would.