"Most libertarians wouldn't think taking a pair of shoes from a store without paying for it was just or reasonable, but when it comes to paying the bills for society, it suddenly becomes just and reasonable to take without paying."
Not at all. This is an absolute straw man.
We have no problem paying for what we use. But we dont want to pay for the things we dont use. Like the wars, the spying, the surveillance. And the things that we do use, we want provided in a competitive market-place where abusive unresponsive or otherwise problematic suppliers cannot simply continue to bill us as much as they wish and use it for whatever they want!
Stability is important but it must not be our supreme value. To do its job a society has to be founded on principles of basic decency and respect for your fellow man. Robbing your fellow man or, if he resists, shooting him, in order to fund your favorite pet project (whether the project itself is worthy or not) simply doesnt fit the bill.
"On the otherhand, I do understand the Libertarian argument that you're taking the fruits of someone's labour to pay for society. But I fail to see how it's any different than paying any other shareholder his fair share of the profits."
Really? You fail to see the difference between a consensual relationship, and a non-consensual one? The difference is clearly in whether or not each individual has the choice of whether or not to enter and remain in the relationship. The consequences of that difference is that consensual relationships inevitably offer a net value to all parties (otherwise consent is not granted or is withdrawn) while non-consensual relationships do not necessarily offer that value, as one or more parties is captive. It seems quite clear, and hardly a trivial distinction.