Of couse this doesn't mean that a bunch of libertarians would be incapable of starting up a volunteer army. Make your case for a defensive force, and you'll probably persuade enough of them to fund it. Voluntarily.
Government-funded scientific research? Nope.
Make your case for government-funded scientific research, and if your case is compelling enough, you'll probably persuade enough of them to fund it. Voluntarily.
Public schools? Highways? Libraries? Parks? No! No way! Never. Nope.
Make your case for government-funded whatever, and if your case is compelling enough, you'll probably persuade enough of them to fund it. Voluntarily.
I hope you're picking up a pattern here.
It always boils down to whether or not you can persuade someone else to do something voluntarily. Non-libertarians, however, seem to feel justified in forcing others to pay for their pet programs. Just how do they justify that? The old "ends justify the means" argument?
You will never get a 100% of agreement. So someone "might be minimally constrain of individual liberty", is that wrong?
80% of us might agree that we need a state highway system and apply a tax. Must we get 100%? If not someone might be constrain of individual liberty.