Welcome to Border Troubles 101. Your friend will join the throng of inadmissables that overfly specific countries that won't let them in. I know half a dozen or more who have moaned about some past episodes, and say exactly as your friend, "Never Again," and they just don't go. They enjoy Mexico, Cuba - the world in fact, except USA.
Your friend could have gracefully exited your company and done what thousands do, overfly what has become their stumbling block. Or perhaps mentioned previous to your travels that he might be stopped at the border. Time does not automatically change things, not in Canada nor in your own country.
There are pardons to be had if acted upon. Too bad the border trouble likely has gotten in the way of that.