Second reply. I actually expected a reply like yours. I've seen them before.
It usually comes from the true meaning of Anarchy and I am a fan of that meaning myself.
Most anarchists also agree that taxation is force, and a form of theft.
The problem with open borders today.
They will go partially towards anarchy when it comes to borders.
Yet they will then also yell that these people that cross the borders should get educational grants, food paid for, medical, housing, etc.
Challenge that and they might call you "racist" even though you don't care what race they are and it is irrelevant.
You see they miss the fact the only way that stuff can be provided is by taxes or debt. If it is debt it is debt taken out against the citizen. So they get the "taxation being theft" idea but they are fine with it if the THEFT allows people that they don't view as trespassers to be supported.
Socialism is great until you run out of other people's money.
If it cannot be done voluntarily it is not a good idea.
We have a lot of bad ideas in the works now. Yet we should be realist and work at eliminating them. Pretending they no longer matter is a recipe for disaster as a lot of the bad ideas come from cultures and how people were educated. They are increasingly educated to treat the government like parents. How often do they say "the government should do something about?" If you want borders not to matter then we should be minimalizing or eliminating the concept of government. Yet for that to work the population would need to be okay with taking responsibility for themselves rather than feeling like someone else OWEs them. They need to know how to use critical thinking to have discussions and coexist with people they disagree with. They need that critical thinking to be less susceptible to propaganda and other common means of population manipulation.
If we get the population there then we might finally be where borders don't matter.
Yet at the moment borders to a nation are as important as being able to lock your house door, or your car door if some neighbors have potentially dangerous types that may or may not respect your property and rights.
Open borders today is pure lunacy.