I have as of yet in my lifetime watched anyone with any firearm training try to show or demonstrate anything with a loaded gun.
It is either with a dummy gun, or you will see them take an unloaded gun, still take the magazine out to verify it is empty, then rack the slide to make sure there is not a shell in it, and then pull the slide back and visually check again, all before using a real gun in a demonstration.
I have watched them do this right after cleaning that same gun and placing an empty magazine in it. When I asked them why, they know it was empty, they just cleaned it. I was told is was a routine or habit that they never want to break, so every gun every time is checked.
That is why we need trained people, whether teachers or not, but hey must be trained, not some idiot like this guy. He had no respect for a loaded gun and handled it very carelessly.
If someone wanst to look at any of my guns, whether they are trained or untrained, if they are loaded, i unload and check them, if I know they were unload when I put them away, I still check and clear them. The reason I do so this is that I do have others who live in my household, and at any time someone else could have loaded that gun. I was taught to always treat every gun as if it was loaded, and NEVER point it ant anything you were not willing to shoot or kill.