Anybody fancy getting back to me on this one?
Well, when you get to the community level, it becomes: "Is it OK to tax the well off to help those that are less fortunate." I think the answer to that question is best debated in another thread (For the record, I'm not saying the answer is "No" I think the answer will be different degrees of "Yes.")
However, if you view it from a state-wide perspective, this is no longer really the "Taking from the fortunate to give to the unfortunate" that will not be discussed here, its taking from one large group of people to give to another (Theoretically) equally well-off group of people. And its doing so on grounds that have very little to do with the people that are paying in.
I don't know why the state-level is the standard, nor do I think it should have to be. Heck there was a (I'm not sure how serious) movement at one point for Long Island to secede from New York because the island is paying something like 3 billion more in taxes than its actually getting. While I certainly understand WHY the discrepancy (Upstate New York is bigger and has less people, so more road coverage for less people) but I don't like it, and, at least in theory, would have no problem with Long Island wanting to secede from New York to correct the problem.
So yeah, its not JUST the state level, you do have a point there. But a state is still a smaller building block of the whole, so to take the same amount of money from all the states, and refusing to give one state the benefits of that money that its people paid unless they change their laws should be considered more or less equivalent morally to making them change their laws.