Hiding behind "liability" is just more security drama. Wonder what he might have said if you had whipped out one of his signed training certificates with your name on it.
Actually, no I do not wonder. Met his identical twin brother/cousin several years ago at a pin shoot. I was told that my training was "out of date" because I had not done yearly re-training with him. As if I ever plan to spend money taking the same class every year, as opposed to looking for training that takes me to the next step in proficiency.
By "discussing" it at sufficient volume the other student candidates overheard and staged a mini-revolution. Get with the program or start issuing refunds on the spot. The mere thought of all those $$ floating away must have been powerful enough to get him to agree to drop back to the proposal that we all agree to "No handling of guns behind the firing line."
Please speak to the gun club administration. If they regularly allow members/guests to remain armed then they need to inform any "guest" instructors that the same is expected of them.