Ahh.. you like being kidnapped from your family and jailed for the rest of your life because you MAY do something in the future?
Hell, with that attitude, kill them, young, old,.. whatever. More cost effective... start a pogrom.. .. hell kill the mothers and fathers for having a mage childdren...that will teach them......
A mage can cause a mini-nuke. That's all fine and all, but they also are open to demonic corruption that makes them that nuke out of their own volition.
Its like if someone could destroy a city. Big deal, most of us could find a way to do it if we tried hard enough IRL. But then again, we don't have people that could snap at any moment, as just one person, and do it, whether they even wanted to or not.
People are widely wary of mages themselves, but not terrified. They are terrified of demons, who prey on mages and make them into a huge danger. Where the Veil is 'solid', and the threat of demonic possession is minimal, mages may walk around nearly as free as anyone else (though with watchers/guards), whether that be in the more Orlesian system or elsewhere.
Everyone is jailed if you want to get down to it. Citizenship, religion, conscription, all ways that restrict movement and action. But not always, or at least it can be loosened. Not all Circles were freakin death camps. Ferelden's Circle Tower was in the middle, The Free Marches' Gallows was the most restrictive and abusive in the world, Rivain's was super lax until outside Templar and Chantry authority freaked out about it, and Orlais' Circles outright allow mages to walk outside freely and operate more like a collage with Templar security guards. The Libertarians were housed there, and the Seekers worked with mages to assist apostates and track down Templars that abused their authority. It was VERY fair until recent events.
Many, mages and non-mages alike, don't really hate the idea of the Circles, because the threat of demonic possession and mage superiority complexes (and both feeding on each other) is very very real. But most would agree that the system is imperfect, and that change is necessary and inevitable. You can decide whether you prefer Circle reform of one sort or another, or an embracing of the Colleges in one form or another. The Circle path (one way or another) means that the mistakes of the past may occur again. The College path (one way or another) means that new mage problems will pop up more often. But the current way doesn't work well enough for the Thedas now and the Thedas of the future.
In a world without demons, or at least demons to this extent as Thedas deals with, preemptive mage control would be automatically extreme. But they're there. This is a world where you could be living peacefully and literally in the same day, your brother in your home is possessed by a pride demon and kills 100s of your town without any warning except that your brother maybe cast a single tiny spell once and you saw him do it.
The elven paradigm was different because the Veil didn't even exist, at least in any recognizable form. It wasn't so black and white, and spirits therefore did not operate so black and white either. The Veil both protects the world from the further extents of magical danger, but also amplifies the problems when it does occur. Like the Templars/Circles themselves, as we see in Kirkwall (the Veil was thin but if Templars were not so control freaky anyway, it could have been okay, etc).
EDIT: BTW, if anyone wants to completely support how Rivain does things, I highly suggest you wait and see. They may be just people like anyone else, and operate safely enough, but I almost guarantee that the practices that hedge mages and others in Rivain employ WILL creep you out, as may the cultural acceptance of these practices. Frequent communion with spirits in a world that is Veiled = openness to both positive Spirits AND negative Demons, and I wouldn't be surprised at all to see that Rivain has mortals but pawns (at least to some extent) of these hedge mages and their spirits. That doesn't mean that things are all terrible, and in fact Rivain may be a nice place overall, but it will not necessarily be the paradise that it sounds like on paper. Both Qunari and Rivain lands give off a feeling to me of 'great community, sucky for individualism or safety'. Just as anyone who doesn't fit the Qun way is dealt with badly, we may find that anyone who doesn't fit the Rivain friendliness to magic/spirits may be dealt with badly as well, and we may find there was a better reason for the Templars to annul the Circle there than we originally thought. NOTHING in Thedas is purely good.
Just speculation, but still..