Confederate flags up north are a thing. They are not common per say but they're there.
I've driven around in rural New England quite a bit, and while Confederate Flags up there aren't exactly common, you do see them. Early last year, I drove extensively in Nevada, Utah, and Arizona and oddly didn't see a single Confederate flag. They may be more common in rural OH, MI, & IN, but I've never driven there so I can't give a first-hand account.
My Ontario neighbour has a confederate flag on his back porch door.
Now that is strange.
Did this person once live in Southern US?
I've never spoken to him. His backyard is adjacent to the area behind my apartment where our little parking lot for tenants is.
The closest thing I can think of is that some strongly pro-gun Canadians might associate "2nd amendment" rights with southern heritage? Or he's a full blown racist (and/or an American immigrant).