Blackwolf,
There is a time and place for everything. I personally don't smoke Mary-Jane but I am not opposed to others imbibing. I do like a beer or a shot of rum. Neither of these come out at camp until the day is done and the firearms a stored for the night. The part that I find most disturbing is the son smoking pot in the field which essentially makes him an impaired hunter.
No matter how sloppy anyone might be the mix of firearms and being impaired is not acceptable. All of the other bad elements aside if you cannot get your friend to recognize that this single act gets his some banned from your camp then he is not a true friend. No one can reasonably argue and defend something so potentially unsafe.
Just think about how the scenario would have played out for him if a Conservation Officer had come onto the scene as he was toking a joint with a rifle in his possession. At best he would have pretty much lost license and PAL. The rest of you would be lucky to come out unscathed. The CO could potentially chose to make all guilty be association and charge others for not intervening or condoning his actions by 'tyring to keep the peace and doing nothing'.
There are many responses here and I pretty much think that it has been decided in the court of public opinion that you have more than accommodating. I bow to your patience as I would have sent him packing as soon as he failed to follow the deer he had shot...