A person desires, at some time, to procrastinate. They know it’s bad for them, but they don’t want to do their tasks. On anti-realism, this is not a rational failing.
I am just picking one of these examples, but an anti-realist could call this a rational failing. People can have many different desires, and thus many different reasons for action, e.g. you could have a desire—and thus a reason—to procrastinate, while at the same time, have a stronger desire—and thus a stronger reason—to work. An anti-realist could say that one is irrational for not doing what one has most reason to do, and in this case, as they have more reason to work than to procrastinate, they are being irrational here. You may say that this impossible, but a “stronger” desires does not have to be defined as being “more” motivational. “Stronger” desires could be understood as, e.g., more persistent desires.
Ah yes, I agree with you that it is not so clean-cut in reality. I also agree that an anti-realist need not claim that it is irrational. However, I just wanted to show a possible counterexample to the author’s claim that “on anti-realism, [procrastination] is not a rational failing”. There is not just one single “anti-realism” and so while not all anti-realists would argue the person is being irrational, one certainly could (with consistency) argue that. And the same could be said for the other supposedly “crazy” examples that the author provided.