Immigration, and customs too, belong to a different body from the rest of us, the two being a different, but closely related, subspecies of humankind!
The US men at the Canadian border have evidently confused the northern border of the US with the southern one, and are equally disliked by Canadians and returning Americans alike. But 'friendly' peaceful Switzerland has the same subspecies. I go through Geneva from France and Britain a lot, commonly en route between the three, staying in Geneva for a day. For some reason, they regard any such traveller as supremely suspect. I have no idea what crimes they suspect us of, except that of wanting to live for 24 hours in Europe's tidiest country, but there it is.