That's even worse - it's a value judgement based on (unverifiable) assumption of person's motives.

It's a value judgment based on behavior observed.

Motives are in the mind, they cannot be verified (even if explicitly stated by the actor, they can still be lies or wishful thinking).

Behavior can be observed however, and conclusions can be drawn.

The idea that it shouldn't be done because it's "unverifiable" is non practical (and somewhat absurd).

> It's a value judgment based on behavior observed.

So it's exactly what I said in the first comment - "lazy" just means "one who doesn't do what they ought to". So it's completely meaningless, except for the part of describing behavior, and cannot be used as an explanation - i.e. "he didn't do his homework because he's lazy" is a circular statement.