It was a prop to him, not a gun.
That is a good point. Lets play devils advocate.
If in fact there was a hazard, in that there was a dangerous gun on the set, why would those on set feel comfortable enough to be have a conversation, as you put it, seemingly unafraid of being shot? Why would everyone just be "going along" with the flow of the day?
I argue: the gun was not thought of as a gun, it was a prop, and props dont kill, normally.
So, to say that Baldwin committed a crime, you have to make the leap to say that HE put the live rounds in the gun knowingly.
I am very experiecned with firearms and their use, and I am on edge when at a range....why? Because of the potential danger.