With respect to proportional contributions: I am not ignoring it. In fact I'm seeking to correct it. You see the rich in our current society, extract far more value from our public systems than the poor or the working class, but they contribute to society vastly less. Their business under a relentless drive for profit deplete our natural resources at unsustainable rates, they benefit more from public services and infrastructures because they own properties, which get protected by law enforcement, they own businesses whose legal operating infrastructure is paid for by public money, the use the courts which are publicly funded far far more than the working class. This is to exclude specific egregious industries whose owners benefit immensely from public resources, such as media companies who broadcast over publicly licensed airwaves and frequency bands, the military industrial complex whose highly lucrative existence is leeched from tax dollars. The rich take more, and contribute less, on a scale that dwarfs any amount of luxurious living by non-working poor you could possibly dream up. A UBI, calibrated to give a dignified comfortable but spartan existence to members of society who don't earn a paycheck, could only serve to reduce disparities in contribution to society, without even beginning to talk about the upward pressure the ability to opt out of working would place on wages.
With respect to some fuck baby being your problem: You just hate the poor. It's okay, I hate the rich. Why should some warmonger jackoff get to make millions off my tax dollars building the next generation of assault weapon to put in the hands of the sons of my neighbors so his jackoff politician friend whose also paid on my dime can send those kids across the world to kill other poor people so a third rich jackoff can harvest foreign oil for profit. Who decided that was my problem?
With respect to benefit derived from taxes: Hey you're right! As outlined before the rich derive vastly more benefit from taxes than the rest of us, and proportionately they do not pay nearly a fair share. So in the name of society being more equal, lets make them contribute more, and then use that contribute to support the poor and down trodden more. Doesn't that sound like the right thing to do?