It's a slightly roundabout set of links that tends to become very clear to people paying >40% of their income in taxes. First, some setup:
The base case is I think the world needs to change, so I spend 8 hours changing it for the better.
The extended case is other people notice I am making the world better, and want to pitch in. We've got this great indirection system in money to allow that to happen with a highly abstract measure of 'resources' so even if they don't know how to contribute personally they can signal how important my work is to others.
Now, there are respectable schools of thought that believe something like (a) there are people who do not have the capacity to meaningfully contribute resources or (b) initial control of raw resources is more impactful than human endeavor. They employ taxes to change how resources are distributed.
And now, the freedom angle:
Without government tax, if I work for 8 hours I can presumably provide for myself in about 2-3 because modern production is so efficient, and then I get 5 hours to reshape the world into something I want to live in. With government tax, the split is basically 2-3 for me, 2-3 for the government, 3 for changing the world to taste. This is effectively a loss of liberty, because now I have half the control over how the world changes.
That isn't particularly profound, it is just how taxes work. But one of the points of money is abstracting direct work for contributing. In a sense, this is the same as labouring directly on a government project for 2-3 hours, and that would be slavery. Obviously taxes aren't slavery because they aren't mandatory (don't want to pay taxes, don't work) but the parallel is there for reducing liberty.
Interesting argument, though I think this could also support the claim that paying taxes increases personal liberty. By having a portion of income paid into the commons for the general benefit of society, this means you don't have to work directly on such government-led projects, giving you increased freedom in where you apply your labour.
I think you're being a bit idealistic to assume that people would generally spend their excess resources shaping the world for the better.
Instead, we seem to see a lot of people spending those resources on shiny toys to make their own lives a little better, and in some cases, spending those resources to ensure that they get more resources in the future, at the expense of others.
The problem is that most people act selfishly with that "5 to reshape the world into something you want to live in". The world they want to live in has them lazing on a beach, not providing healthcare for the masses.
