When I protested and gave them the handout of their own procedures, the guy said “you can give me the key, or you don’t get on your flight.”
They did that to me once and when the Agent showed up at my gate with that line I replied that I was happy to tag along back to the case and open it for them. The Agent took me the back way through the service halls to their area where I opened my case and they did their inspection, then they brought me back to the gate through the service halls.
The agent wasn’t happy about it but I stayed cool with 'em and they made it work.