Mathews, I have the upmost respect for customs performing there job to protect our national security, as long as its not a personal/justmental attitude, if an agent is having a case of the A$$, as you say who is overworked or may be missing their family, but you guys have to see it from the law abiding citizen that is trying to see a love one that is under going chemo/ect. across the border and then I got to play customs games by your rules, I am professional in my line of work and expect that professionalism that goes with the badge, I have lived in British Columbia for over 5 yrs as and and now in Montana and have crossed the border back and forth, since I live only 6 miles from the border, I am not new in dealing with agents on both sides and I can only tell of my own personal experiences dealing with customs, you can tell me how difficult you guys have it, but you guys have to cover your A$$ too, but what I am saying is there is a diplomatic way to greet visitors at the border other than say turn your engine off and show proof of citizenship, when you put people on the defense with these statemates , don' t you think its puts them in a position real quik to get defensive, even for someone who may be in the right.
I really dread going across the border and the reason being is dealing with agents, since 9-11 I have seen some newbies at the border a lot of them lacking in diplomacy, I wonder whom is on duty and if I am going to be detained, is it going to take a minute or is this agent going to have a case of the A$$ and and put me through the inspection lane chequeing my gas tank as he is grounding my truck, he has got all day and takes his time and then another agent questions me and removes my hat and is chequeking the brim inside my hat maybe looking for a joint,ect., I try to be as patient as possible, but as you say a persons body english will speak, It seems like I have absolutely NO rights at all when I cross customs and you you guys have a open ticket to have a case of A$$holism, and the sad part about it is I can' t do didley squat about it, just play your games.
No disrespect intented, I cross the border quite a bit and call it as I see it.

Been there and done it, Bobby