In a world with a $10K yearly UBI, income taxes for many people will go up by a lot more than $10K.
If someone proposed a policy where everyone who makes under $1M gets a free sandwich, that everyone who makes over $10M pays for, the only people who sensibly should be against it are people who make over $10M or people who think they might one day make over $10M. Nobody else would ever have to pay for it--why would they be against it?