Although they should have let him write the review, I don't think people should leave reviews for damaged/broken items before they've tried to remedy the situation with the supplier.
Or maybe the product just has poor QC, again, it should be allowed to show up in reviews.
If it's just a one-ff then it will be watered down by all of the other reviewers anyway
Also, perhaps a higher percentage of people with bad experiences will write bad reviews than people with good experiences writing good reviews, so the watered down argument isn't perfect. I would have left out the word 'perhaps' but I don't actually have any hard evidence.