It seems there are a couple of airports that are worse than others. I'm going to break tradition and use city names instead. Much like any country, each city in Canada has a different "culture". Calgary has had numerous incidents of what one might call "abuse" of overzealous screeners. Montreal has attitude but is still professional. Toronto is larger, loud and busy. You'll get fewer "Canadian" niceties there but they are still professional. Ottawa is fairly innocuous. London is much the same. I can't speak for Vancouver or any others at this time as I've not flown out of any others in years.

I can understand how flying in the US, or even hearing what's going on, would make you especially sensitive or nervous about the any CP experience. Best of luck in whatever decision you make and hopefully your trip is a good one.