How to prove Socialist don't believe in Socialism
Think about the upside:
- It fixes the balanced budget problem (they only get to spend what they earn: except the military during a congress declared war)
- Politicians have to champion to the taxpayers the good they're doing to get people to contribute
- Wasteful stuff gets called out, and punished. 
- The budgets self correct for what people care about most
- No one has to feel like their money is going to things they morally/religiously disagree with.
You support government sponsored abortion, or you believe in border security, you can pay for it, and let others opt out. The statistical averages will keep things from swinging too wildly, and it allows more diversity of thought. I'm not against someone else spending their money on things I disagree with, I'm just against them making me support it.
The wiser the community spends the money, and the better the outcomes... and the better people will feel about contributing. And the more they will contribute (to those causes). It puts incentives for performance back into the system. And it doesn't have to be dollars, you can contribute in time to offset your taxes if you want.
It teaches the community to value contribution and education (over time). Individuals with more kids (or grandkids) will contribute more, those with fewer, will contribute less. Districts and communities that don't contribute or manage poorly, learn the consequences.
Society grows and becomes better because of the examples they create.
The people that are most outraged at the idea are often the most left/socialists. Why?
I get answers like:
- "You can't trust people to contribute voluntarily, you have to force them!"
- "But everyone should have to contribute to the causes I like... it's the ones I don't like that are the problem!"
- "if you let people have freedom of choice, many will opt out and do the wrong thing (not pay)... and be rewarded for it!"
And bam -- they just accidentally exposed their true beliefs.
What they just admitted (without realizing it), is that Socialism/Communism is not about the community working together to do anything, it's about the minority forcing the rest to do something they wouldn't do otherwise, because they fundamentally don't believe the community will do the right thing without force.
If they believed in individuals or the social norms, they would trust that a voluntary system would work. That they don't, proves that they don't believe in socialism, they only believe in tyranny! Socialism is about bullying others, not about democracy, choice or community. No backsies.
Of course the truth is that most just get mad, and refuse to learn the lesson that they were just offered. Face it, if they could grow, they wouldn't be socialists in the first place. But it's still a fun example that seems to work every time. And their tantrums and distraction when you catch them in it, just drives the point home.