They gotta keep the criminals out somehow. I know quite a few well to do white men with DUIs that kept them out of Canada and I can't blame Canada for it. I think any Felony will keep them from letting you in.
Which is why Trump should be banned from entering as he is a convicted felon.
It’s a bit more complicated than just “any felony” - among other factors, Canadian immigration law considers how Canadian criminal law would treat the offence, as well as how long it’s been since the sentence was completed. And there are discretionary provisions to allow ministerial overrides, as I’m sure they’d do for Trump during his presidency if he would otherwise be covered.
But you’re right, it’s absolutely true that Canadian immigration law treats DUIs by foreign nationals far more harshly than US immigration law does (assuming simple DUI in each case and not something with complications like someone getting hurt or killed).
Which is why Trump should be banned from entering as he is a convicted felon.