I see a very big similarity between minarchist libertarians and communists (especially anarcho-communists):
a) Minarchists consider the state as a way of preserving “the rules of the game” that should prevail in a free market, i.e. freedom of contract, pacta sun servanda, punishment of fraud, and especially the preservation of private property
b) communists (especially anarcho-communists) consider the state as a way higher classes have of exploiting the poor through the preservation of private property.
I know minarchists consider the preservation of private property as a good thing whereas communists consider it the root of all evil. However, both ideologies share a same underlying assumption: the state is necessary in order to maintain private property. As long as the state and a degree of private property coexist at the same time we must acknowledge that Marxists have a point (or at least we can’t prove them wrong) regarding their consideration of the state.
And this is when anarcho-capitalism comes to play by considering the state not the friend, but the natural enemy of private property. For me, the relevance of anarcho-capitalism is that if a society could exist for a long time without a state and with private property, improving the standards of being of all, including the poor, (as I believe it would) it would tear apart and make senseless those marxist statements. On the other hand, if a minarchist free market society existed for a long time, communists would still have a point (or at least they wouldn’t be proved wrong).
I know some might say that the difference between minarchism and anarcho-capitalism is not so big (all in all, one favours 95% freed markets and the other favours 100% freed markets), and although I somehow agree with that statement, it is also important to note that that small percentage is highly relevant when it comes to disproving Marxist ideologies.
Why single out minarchists and anarcho-communists?
Couldn't it be said that everyone except for anarcho-capitalists believe the state is necessary in order to maintain private property.
Your're right, it could be said of any or almost any other ideology.
I'll say this... the arguments made by the far left that a state is necessary to help the poor are just as ridiculous as the notion that private property can only exist if an irrational agent violates your rights. They have irrationality in common.
They're both statists.