Well, that's tough to say. I think I would have talked to the guide first about your concerns. A quality guide isn't going to let just anyone go out start flinging arrows. After all, he's the one that's going to have to go in after a wounded bear. If the guide saw that guy shoot and let him go anyway, well that's foolish in my mind.
If the guide refused to say anything, I think I'd find a way to give the fellow a little coaching. If he was resistant to that, well, that's all you can do.
Unfortunately, the world is full of people that won't take the time to become proficient enough to hunt. And it's not just traditional archers. I've got family members that are like that. It's incredibly frustrating to have them ignore advice and offers to help them shoot better and then listen to how they "got a shot off" or "I hit him but we didn't find him." All we can do is diplomatically educate them.