Also is the concept of “reasonable person.”
Is reasonable to assume that a person would pick up a rifle/pistol and then play with it and in the process, point it at another person and pull the trigger?
No reasonable man would do that. Therefore, the fault lies with the shooter-—he was acting stupidly. He was acting unreasonably.
You just flunked your first year of law school. The question is whether the owner acted reasonably in hanging a loaded rifle on the wall in plain sight in decorative fashion, knowing that a large segment of the population is too stupid to get out of bed in the morning (as evidenced by the results of the last election). This is no different than storing a can of Drano next to the salt box in the food pantry: Reasonable people recognize the potential for stupidity and take reasonable steps to prevent injury to invited guests. That means storing dangerous chemicals out-of-sight in a safe location with other chemicals and it means removong the ammunition from a firearm hung in plain site as a decorative object (or at least placing a warning sign on the gun).