The thing is, this minority wouldn't be treated the same way if it wasn't a minority. Or you do think that people would put up with being imprisoned for all their lives as a rule? That they would meekly agree if it was *they* who were to be imprisoned? For others - for those perceived as "other" - it is apparently ok. Thus, we don't have a system that just implements necessary security measures, we have a system of oppression.
No, I would not want an untrained mageborn child to live next door to me. That's why I've alway supported mandatory training - perhaps that wasn't clear on my earlier post. But I do, in fact, trust my neighbours not to bomb my house, go on a shooting spree or turn into serial killers, as a rule. I would trust a trained mage not to go out of control the same way, and yes, I would have no objection to one being my neighbour - or my lover. Yes, the bad stuff happens nonetheless, but I'd be quite as defenseless against a suicide bomber or a trained soldier gone mad as I'd be against a fireball-slinging mage. Yet we don't imprison everyone who might go mad and turn on their neighbors - meaning everyone - do we?
Also, it does matter who does the goalkeeping and policing. In the Circles, mages are kept by representatives of an ideology that has "keep mages under [your] control" as a consequence of its core tenets. That's like recruiting the American police force from the KKK. Seems exaggerated? Consider what those people's agenda is: "Keep majority faction X in control and minority faction Y controlled" and remember that they see their cause as perfectly legitimate. This illustrates neatly that it does, in fact, matter, who does the policing, and that warriors selected, among other things, for their ideological fervor may not be the best choice.
Not that the mageborn are unique in being kept under control by an oppressive system. See Orlais and its elves. Compared to them, the situation of the mageborn doesn't appear all that bad. However, as I said before, "It isn't that bad" is no argument against autonomy. There *is* no argument for denying someone autonomy but a necessity that weighs higher, and any system that goes beyond mandatory training will justifiedly be regarded as oppressive.
The presence of magic will always mean that there are more dangers compared to a non-magical world. How far preventive measures can justifiedly go will always be a matter of contention. However, things get complicated when real dangers and minorities which are perceived as "other" mix, like in the case of the mageborn. In the real world, people object to rapists who have served their time in their neighborhood. However problematic I find this sort of behaviour, they have a better cause than one who objects to the presence of a trained mage who has done nothing harmful to anyone so far. Beyond mandatory training, I see no reason to break with the principle that people are free unless they do something that requires intervention.
1) If mages were the majority they absolutely would oppress the normal population. The inevitable consequence of having a large segment of the population that has so much more potential for power is that without restrictions they will eventually use their power to place themselves above all others. This doesn't require all mages to take that stance, only enough of them to rise the top. And the most ruthless will always be at the top because they will always be the most powerful.
Every society in Thedas that has free mages is at least in part ruled by them.
2) Comparing mages to any real world minority is a false equivalence. No real world person presents the same danger as a mage does simply for being part of a minority. The suicide bomber, the serial killer and the soldier all need to have the skill, the equipment and the desire to become a danger. A mage does not, he simply needs to be a mage. Would you support allowing random people access to bombs and guns? People who at any time might be compelled to use them against friends and family by someone else's will?
3) Even fully trained mages present a legitimate threat to the public that a mundane doesn't.
Wilhelm was an example of a fully trained mage allowed to live outside the tower and raise a family and he summoned demons in his basement during his spare time.
Orsino was an example of a fully trained mage who became a danger to his allies because he decided that hurting his enemies was more important than protecting his people. Yes, he was fighting templars at the time, but it could just as easily have been bandits, darkspawn or a foreign army.
Adrian was a senior enchanter and she nearly set a peasant on fire because she didn't like his views on magic.
Rhys, another senior enchanter has a moment in Asunder when he thinks about how easy it would be to tear the veil and set demons on his enemies. He pulls back, but the temptation was there and a slightly less restrained man would have succumbed to it.
And of course, if the old Tevinter Magisters truly were responsible for bringing the Blight to Thedas than those seven mages unintentionally caused the deaths of more people than have ever lived in the Circles.
When a mage, even a fully trained mage is just one bad day away from becoming a threat to hundreds, I prioritize the safety of the many over individual freedoms.
4) The KKK reference is most definitely an exaggeration that serves only to attempt to inspire guilt and moral outrage.
The purpose of the Templar Order is to protect innocent mages as much as it is to contain the dangers of magic.
And this is the Chantry's official stance on magic:
Magic exists to serve man, and never to rule over him.
Foul and corrupt are they
Who have taken His gift
And turned it against His children.
They shall be named Maleficar, accursed ones.
They shall find no rest in this world
Or beyond.
It specifically condemns the use of magic to harm and control others. It does
not condemn magic in general and even calls it a
gift, not a curse as everyone likes to claim.
May I mention, again, that the fundamental desirability of prevention does not mean any cost we pay in freedom for preventive measures is necessarily justified. The same applies to "any power an individual might have is only acceptable if it can be easily countered". Beyond controlling weapons of war, human societies dont work that way unless they're totalitarian. I can already anticipate the rejoinder that mages are weapons of war, but (I) they actually aren't without a steady lyrium supply, and (II) they're human beings with the same rights - if such are said to exist in their culture - as other human beings. Things get even more problematic if the people in whose names the measures are implemented don't have to pay any of that cost. That's a perfect recipe for rebellion if ever heard one. I don't think it's coindicence that most cases of possession actually happened within Circles or to escaped Circle mages on the run.
5) The power of mages far outstrips the power of a common man. They are absolutely weapons, even without lyrium. You vastly underestimate the dangers of magic. In game mechanics, we can shrug off fireballs and nothing around us is damaged. Realistically, that's third degree burns in a world without antibiotics or skin grafts and an out of control fire in a world with no running water or fire extinguishers.
6) People don't like being locked up. In other news, rain is wet. That says nothing about whether locking them up helps a greater amount of people than it harms.
7)
Of course it isn't a coincidence that most abominations come from the Circle. Most mages we meet are inside the Circles or running from them. You may as well say most elves are City Elves or Dalish. It proves nothing. You can easily replace those situations with any dire circumstance a mage might face. For instance, the fear that your sick father would die.