How would this differ from the tension we have today between the employed and the unemployed? The latter are already heavily stigmatized (dole bludgers, welfare queens, etc).

How would it increase inequality?

those who choos 40hr work weeks have similar earnings and quality of life as someone who sits at home all day on UBI.

Why do you think the word "universal" is in the phrase "universal basic income"?

then it will never happen, of course. keep fantasizing

No? Everyone would get the same amount, and then the people working 40h would get more than the people not doing anything.

Absolutely not. Our current system is closer to that because you lose benefits as your income increases, to the point where in some case it's possible to get a raise and end up worse off. With UBI (assuming it replaces most means-tested benefits), you're always better off earning more.

a definitive assertion offered without elaboration

It would do the opposite.

It would set a minimum income that everyone would know they had.

Whatever work people did would add to that. It would encourage the unemployed to start businesses, or do casual work as they would keep all the money (rather than having their benefits cut).