Well, the part you are leaving out is, my guess is your friend had a serious felony conviction, back in the day. You use the term indescretion, I doubt he tped someones house. And that was the crime, for which Canada barred him
Canada tends to take a dim view of such things as felonies. Had your friend not lit up their computer screens, you would have been waved through with a friendly nod. I live in Seattle I have crossed that border at least a 100 times. So I have some experience.
Think it's tough getting into Canada, Nope getting back into the USA is the tough part