Out of all the people that know 100% Baldwin is guilty of manslaughter, how many would flip their opinion in an instant if Trump killed someone while filming a pro gun campaign ad?
A learned intermediary handed him a dangerous tool and said it was good to go.
If the pharmacist gives you the wrong pills filling a script for your kid, and your kid takes them and dies, you're not liable for manslaughter.
It is generally reasonable to rely on the professional representations of a learned intermediary, especially in a case where the intermediary's profession is so life-and-death important.
This was the armorer's one contractual duty. As a producer, Baldwin took reasonable steps to protect the victim by hiring a professional armorer. That satisfies a principal's nondelegable duty for general safety, imo. Maybe he is culpable for negligent hiring or negligent supervision, not for manslaughter, though.
Further, what are you saying was Baldwin's duty, here? To--after the person hired solely to inspect, load, and handle the guns, handed it to him and said it was safe--clear the chamber, take out the magazine, and inspect and reload each cartridge? Baldwin's duties are those of an actor, not an armorer.
If you hire a painter, does that impute a duty on your part to test the paint for lead? No, it's the painter's duty to perform her contract as a reasonable tradesperson.
If he was a non producer, then you would have a stronger argument, but as a producer he may have been negligent in hiring someone unqualified.
In a normal setting, pointing a gun at a person would be negligent, even if you believed it was empty. I don't know the industry standard on movie sets, but pointing a real gun at a human when not in a scene would be at least careless, possibly legally negligent.