"Work" means we know we're doing something valuable to society because someone in society is willing to pay for it. If we're doing something nobody values enough to pay for then we may well be contributing nothing of value to society.

> we're doing something valuable to society because someone in society is willing to pay for it

This is where you are completely wrong. I'm not even going to bother explaining, because there are too many obvious counter-examples.

Why does his choice for how to spend his time offend you so much that you need to directly, overtly insult him for it?

Do you feel a need to control him because his values apparently differ from your own? Fortunately there is no one right way to live, no singular correct set of values.

The ire is because they are saying this in a context where they are implicitly talking not just about their personal preferences, but furthermore about the opportunities that should or should not be made available to others. They are saying this in a context where it functions as an argument against Basic Income, on the grounds that leisure is bad and everyone should be made to work as much as possible, to provide as much for society as possible.