As has been stated many times on the BOI, a seller can have countless positive transactions, but it is how they handle that one bad transaction that matters.
Although the damage to the shipping box does fall on the carrier, I think it is very unprofessional for any seller to tell the buyer it is between the buyer and the carrier, or just chalk it up to the carriers fault and feel it is not their problem. For me, in every case where a package was damaged, the seller made it right, no questions asked. If there was an insurance issue to deal with, the seller handled it with the carrier, especially since a claim can not be initiated by the receiver.
If a seller ever told me I had to take it up with the carrier, or felt no obligation to make it right because "it was the carrier's fault", it would be the last time I ever dealt with that seller. IMO, until the product arrives safely at my doorstep, the seller is ultimately responsible. Whether I am selling live animals or supplies, that is how I operate and I expect no less in return from others.