This is what happens when people don't read carefully. By OP's own admission, nobody "scolded" anybody. She simply used the term in the thread title and will hopefully change it.

Nobody told OP's husband that he could not check the box.
Nobody told OP's husband that he had to sign a waiver.

Nothing has changed. Perhaps the counter agent, I don't think that a TA was actually involved, should not have been helpful and said anything. If the box arrives undamaged, that's great. If it arrives damaged, the claim gets denied.

If you are either willing to accept the risk of damage or are certain that the boxes you select are damage-proof, quit worrying and check away.