Assuming by default that somebody would break the law, just because you politically disagree with them, is not justified. As said above, CC holders are among the most law-abiding citizens (this is true in my country too). They're aware of the laws governing their permit and assuming by default that they'd break other countries' laws is preposterous. You don't just forget that you're carrying when you travel abroad or by airplane. And you sure as hell don't do something as idiotic as that, with the accompanying consequences, intentionally.
As far as forgetting that you’re carrying, numerous examples say otherwise. Random data point: the TSA confiscated over 4,000 guns last year, of which I imagine approximately 100% were inadvertently packed by innocent people. Whether it’s intentional is immaterial; Canada doesn’t want guns crossing the border, and they couldn’t care less if you’re doing it by accident.
If the Canadian border authorities are searching your person, such that they are likely to notice something like a concealed carry permit, your border crossing has already gone south.