nutwood, I like your question, but my answer may not really help you.
First up, all law-enforcement officers (whether it be police or customs or the local fisheries guy) operate within specific and strict legislation. Knowing the scope of your powers and duties and responsibilities is the greatest component of the training given.
Within the police, for example, there is no power to just "take someone to the office". Police coercive powers involve two distinct scenarios - in certain circumstances you can either "detain" or "arrest". These are actually two very different beasts. If a person did not wish to voluntarilly go to the station for whatever questioning, etc, and you did not have a power to detain or arrest, then no, you would not take them.
But having said that, there are many circumstances in which a police officer actually does have the power to detain and search someone. And under many acts (for example those related to transport) the officer has the power to require you to tell you certain things, including name, address, etc. If you fail to answer you are actually committing an offence, even if you had done nothing wrong whilst driving.
When you deal in law enforcement you soon realize that the wider public is, understandably, unaware of all the detail. Of course they are. In Queensland, for example, you can get arrested under two broad categories. The first (and less serious) is for what is known as a "simple" offence - this means it is something that will get dealt with by a Magistrate, not a full-blown judge and court. Stuff like being pissed and getting into a fight on the street ("disorderly"). Almost every drunken idiot that I arrested for this would demand his or her "right" to phone a lawyer. This is an idea they get from watching too much American TV. There is no such right. For a more serious "indictable" offence, yes they do have a right to contact someone. Try explaining that to someone who has just had 20 bundy and cokes
In relation to the searching of a phone, I do not believe that happened in this case. My understanding is that the person subject of the search was asked to surrender their phone, which would seem a perfectly reasonable thing to do for anyone being investigated. preventing anyone from alerting someone else to security proceedings seems valid to me. Again, I do not know customs procedures.
As far as the "turning them loose" only saying "we are just doing our job". I understand the desire of people to want to know why they were detained/searched/etc, and I suspect that communication skills are lacking in many staff in many agencies, but what really would you expect? That they tell the person that "we selected you because our selection criteria involves x, y, and z" That would just be destroying their intel system. I do really understand the frustration or anger this can impart, but there is no perfect way to manage this.
As a police officer I was very proactive. I cared for the community, and performed my duties with zeal. But I was also very aware of the power I held, and tried to blend both the need to be active, with the reality that most people I would encounter were honest, good, people. I strove to find that perfect blend where I could get the job done, but also not make good people feel violated. Basic humanity and compassion and friendliness goes a long way there - I am sure almost all people I did "random" late night intercepts and searches of actually came away from the experience feeling good, positive. But it is an art. And do not for a second forget the human factor - police, as all law enforcement types, are just individuals. Humans. When you get pulled over for a random breath test in the middle of the night, be aware that the person who so coldly comes up and shines a light in your face possibly feels fear. Every so often you pull over a car where the driver is out of his mind on drugs and tries to kill you. And the bad ones could be white or black, man or woman, teenagers or pensioners. Maybe different from the area of Border Force, but similar principles apply. They are actually "just doing their job". And their primary job is not to make people smile. If they went too far that way the actual needs of the position would suffer.
Just as an aside, but perhaps further enlightening to you to how hard enforcement is, I will share a story from yet another previous life, when I worked in "fraud control" for the Department of Social Security.
DSS, as it was called back then (is it still Centrelink, or has it changed name yet again?), is a very serious part of Australia. There are very few countries that have the finances or desire to provide the incredible safety net that we have here. There are immense sums of money involved, so the government obviously puts a great deal of emphasis on trying to manage that. And the powers we had, were, quite simply, incredible. Far more invasive than what I had as a mere copper.
A huge area of rort is people who claim to be single (sole parents, etc) and get a welfare payment, even though they really had a partner who worked, etc. Even if neither is working, payment rates were higher for singles, which many tried to get. So to combat this DSS had great powers. The principle thing one had to determine was whether the person was or was not in a relationship. The basis of investigating this was a specific questionnaire - set questions. These included (and the person HAD to answer these) was if you are having sex with person XYZ. You just cannot get more personal than this. JohnK would have a fit
But I worked in a suburb of a certain city that was predominantly ethnic - ie immigrants. Many to whom english was not yet even a second language. So we tried to get by with interpreters. The vietnamese community was especially difficult - almost no english skills, almost no real documentation (even dates of birth), etc etc. A fellow worker went out to conduct a "review" of living arrangements that had been triggered by a computer-driven data matching algorithm. So the poor bugger had to question an elderly woman and an elderly man to establish their living arrangements. He dutifully went through the form and the involved questions, until it all exploded. Through his interpreter he suddenly realized he was asking a woman and her father if they were having sex.
This is horrendous, but for the life of me, working in the industry, I realised there was no fault on anyone for this event. You can desire perfection, you can do your job in the best way you can, but things do happen. And you get leapt upon.
I am not saying that the Border Force staff are all angels. It is a cough job that will have a mix of great staff who have a genuine love of their work, and others who just need a job. Everywhere in society is the same.
But if you treat the good staff as idiots, you will get back the same. Karma.
Sorry - I have rambled on too long