I would argue that it is in no way a formal part of the process but rather a symptom of the culture in that industry. There is no written policy that says they have to be disrespectful. They dehumanize people and see themselves as superior, this is the result of essentially giving a group of people extreme power in much the same way as the Stanford prison experiment. They have very little limits on their power within 100 miles of the US border, essentially able to do as they please. If they overstep their bounds, their is generally no punishment.

There is no reason they cant do the same job while treating everyone with respect. When you work with a group of people that see themselves as hammers, everyone else is a nail.