Yeah, it's crazy, I feel like it's been some kind of pre-programmed talking point. Say with a 10% VAT, even if you eat all of that in sales tax (which you won't, companies will eat it too), you'd have to spend 120K+ a year to offset, say, $1K/month UBI.
Not to mention that many variations of UBI proposals specifically exempt the kind of purchases most lower income people make most often. You can easily exempt normal groceries, clothing under a certain value, rent or utilities under a set value and many other essential items. UBI can be easily shaped to target luxury purchases.
i.e. polluting cars, red meat, airplane travel, etc... etc...
The problem with 'sales tax' is that are regressive. You are essentially taxing the millionaire and the homeless guy with the same rate.