Several years ago, we had a steer get his head stuck in the tie rails overnight, at a major show with a terminal premium sale. Don't know how long he was stuck there, he was out when we got there early that morning (he'd been in there long enough to dig a big hole), but one side of his neck had a basketball sized swelling, the other about softball sized, and he couldn't hold his head up to even a normal relaxed level.. The show vet came and looked at him and promptly prescribed banamine, dexamethasone and naxcel. I told him we didn't expect to show him at this point, we could take him home and wait out any necessary withdrawals, but he said wait and let's see how he gets along, maybe you can still show him - if he makes the sale he won't be slaughtered for at least 5 days - that gets you past withdrawal on all of those. Since I couldn't see him even being able to show, I went ahead and fed and watered him all he wanted, 'cause I just wanted him to feel better. He was much better by weigh in, so we went ahead and entered him, but he weighed 1440. By show day, if you knew what you were looking for he held his neck a bit funny, but otherwise looked fine - he got pulled 3rd, and when the judge walked his top 5 and checked weights, we dropped to 5th, missed the premium sale by 1 hole. The point of all this is that something very similar happened to us, and we showed, and did not then nor now feel guilty about it.
The official show vet prescribed it - if it's wrong, it's on the vet, not the exhibitor.
Now, all that said, in our case the official show vet was a horse vet - he wasn't used to treating meat animals. I have no idea if he knew banamine and dex are two of the biggest no-no's in the livestock show world. I knew, but as I said, when he prescribed them I didn't think we'd get to show him, and was fully prepared not to, but he assured us over and over that there was nothing to worry about... Without knowing any more than we do about the Calgary situation, it sounds to me like this one's on the vet too.
I fully agree that the safety of the food chain needs to be one of our greatest concerns. But if an official show vet prescribes a substance that's going to get the exhibitor kicked out and still let them show, then the vet and the show need to take responsibility for their own actions in the matter.