>No matter how you arrange your basic income scheme (and the tax system to support it), it's going to split the population into two groups: those who are net recipients of government money, and those who are net contributors.
When the idea of basic income is boiled down entirely to dollars and cents, sure. But, because of the volatility in the labor market, there isn't a way for an individual to know or predict whether they or someone else will be a net giver or a net-taker, as these things must be measured across a person's lifetime. J.K. Rowling was a taker for years, now she's wholeheartedly a giver. These status are primarily self-assigned and perceived based on.... well, I'm not sure what they're based on. See the author's 'popularity' argument, see the interviews with people who are anti-welfare but pro-mincome for themselves.
It's also worth considering -- as every discussion of UBI brings up -- the incalculable, invaluable net effects of such a scheme (and indeed of welfare itself). There are intangible benefits that are unnoticed even to the 'net contributors' -- that is, people who are housed and fed are less likely to stab you in the street for your iPhone.
>Don't let basic income advocates evade the question of who pays for their utopian scheme.
If a particular advocate of UBI doesn't include the tax increase in every point she makes about the system, it's only because that's a given, and has always been mentioned in some other comment. If you believe a particular funding scheme is flawed, have at it.
>you imply that others are obligated to provide them with that income.
UBI doesn't imply that others are obligated to provide them with income. It's explicit in the system. Unless you believe all taxation is theft (in which case: Game over, you'll never come around to UBI), it's safe to say that you believe 'society' has some obligation to the health and safety of its members. UBI is just the free-market expression of that: Rather than have the government try to create a massive, bloated system that tries to predict what people need, give them the tools they need to get it themselves. That tool is money.