A few of our club members, myself included, keep a copy of the RCMP pamphlet on the requirements for safe storage and transportation of the different classes of firearms in my shooting bag.
I really doubt producing it and suggesting, even tactfully, that they read their own policies would be popular, but it may prevent your gun from being seized, unjustly or otherwise.
I'd suggest stopping in at the local detachment and requesting several copies of that pamphlet. If it's only one officer that's the problem, requesting copies of that pamphlet may raise a few eyebrows and get some questions asked all by itself. If it's a detachment-wide issue, that would be harder to deal with, but not impossible.
Document number is CAFC 1238 EF (2008/10) V2
There may be a newer version available now, but I don't think that part of the law has changed.
As I said in my first post, I usually trigger-lock all my guns during transport anyway. I'd really rather not have to face a thief that broke into my car pointing my own gun at me. The trigger lock won't stop them forever, but it'll slow them down.