Yes, I think so. The boy said he didn't know what to write. I have a third grader who wouldn't either. A question like this throws him for a loop. It's the way his mind works. It's an impossible situation and he'd be entirely confused. Insisting and threatening would likely bring him to tears. Again, it's just the way his mind works.
Give the kid a zero. Fine. But someone at the school whose supposed business is education needs to get a clue.
My kid has Asperger's syndrome aand would totally freak at such a question on a test...his reasoning would be the same as that kid's..."I couldn't write anything that they would like to hear so I can't write it"
And no amount of threats, punishment, pleading or begging would get him to do it unless I worked with him to find an angle on that assignment that would not be a threat to him personally!