Good point. Maybe you should tell that to Fiona, the one who sold them into slavery in the first place. 
Fiona agreed to 10 years of service in order for her people to become free citizens of the Imperium,a country where mages aren’t looked at as abominations just for the bad luck of being born different , just as Hawke and his family did one year in order for his family to be allowed inside Kirkwall. But maybe I don't really know what slavery is, let me check for a second:
slavery
/ˈsleɪvərɪ/
noun
1.the state or condition of being a slave; a civil relationship whereby one person has absolute power over another and controls his life, liberty,and fortune
2.the subjection of a person to another person, esp in being forced into work
3.the condition of being subject to some influence or habit
4.work done in harsh conditions for low pay
Let’s see how the Cirlce/Chantry treats mages:
-any child found with magic is ripped from his world/life/family and imprisoned in a building, some for the rest of their natural lives. Well, those who kiss ass(Whynne), spread their legs(Vivienne) or are rich or have powerful relatives(Bethany Hawke and others) might see their family(if the family chooses to visit, they live in a prison after all) or daylight from time to time, but very few.
-the templars have power of life and death over them, and the ones in charge often side with the templars in any issue between them, even if the mages are in the right.
-if they do something bad the templars can choose to turn their brain into mush, making them emotionless slaves.
-and talking about emotionless slaves: the tranquil are still under chantry/templar control, although they can’t do magic anymore, the only reason the templars have to keep mages locked up. Why? Money, of course, since the tranquil can create enchanted items, them being the biggest earners the Chantry/templar order has. It’s strange that there never is a shortage of tranquil to do their work for no pay and since they are brain dead, they have no say in what the templars do to them.
-if a Circle mage has a child, said child is forcefully taken away and given to the chantry, where he can either become a big and strong templar raised from birth to hate his parents, or another slave if he shows signs of magic.
-in Kirkwall the things get so bad, more than half the mage deaths are suicides(we find that out from conversation with Anders), and you can’t say that it’s only an isolated incident, since the mage torture goes on for almost a decade, enough time for the higher ups to find out about it and change something if they cared to, which they don’t. Why? Because Meredith is supplying the Chantry and the order with a huge numbers of Tranquil, which in turn makes them very very very rich.
And let’s not forget that the templars are people who willingly choose to become drug addicts, to the point where they can’t even function in society. But it’s ok to have an order of mage hating drug addicts being the sole caregivers of an entire prison filled with people that can channel, many of them children that can’t even defend themselves, not that the grown-ups have any chance of themselves either if the templars decide to do whatever they like to them.
And let’s not forget how the game decides to make us hate mages in DA2. Anders, a man that spends his entire adult life fighting for mage’s rights, protecting good mages for prosecution, fighting the blight or healing the poor for free decides that he has to blow up a church filled with innocent people.
Honestly, if the game decided to make him an evil terrorist out of the blue, he could at least blew up Meredith or the templar barracks. But no, because the plot demands it that the mages have to do something terrible for no reason other than to imprint in your subconscious the fact that all mages are evil, even the ones that were until that point a good choice for sainthood, and they all need to die or be kept as slaves. Like the 500 blood mages you had to kill during the game even as a mage sympathizer weren’t enough. Honestly, it’s a miracle Meredith had some mages left to terrorize.
Another point I have with the way the Chantry, and by extension the templars treat mages is that they never tried to come with a better solution. A way to cut them from the Fade, by ritual or enchanted item or whatever, or a more humane way to treat them even if they must be watched. But fixing the issue with the possession will mean that they will lose the tranquil and their main source of income, so slavery and torture it is.
Yes, the mages can be dangerous under severe circumstances, but since 800 years after the Circle was created the possession is still a problem, proves without a doubt that the Circle idea is broken.
They need to find a better way to do things.
And lastly, the biggest issue I have with the Cirlces of mages:
The Circle was created because some religious fanatics took the racist/mage hating rant in chant form of a girl born 1000 years ago that stated that magic is bad because the voices in her head told her so.
Not going to even touch on the possibility of Andraste being:
-tricked by a Fade demon;
-triched by a dreamer;
-tricked by Fen’harel;
- tricked by the soul of Dumat that Mythal placed in her
she is born in -203 Ancient, the same year the first Blight ended,
she hears the word of the Maker, and Dumat might be the name the Tevinter gave to one the sleeping dragons(a form the Creators, the beings worshiped by the elves seem to have) that they found in the conquered elven temples, namely Elgar'nan, after they discovered that they can talk to them in the Fade and they can learn super awesome magic from them.
After all, they couldn’t keep the old names they had, it would have been too plebeian to convert to the religion of the slaves they just conquered, so they chose to ignore reality and replace it with their own, names included.
Anyway, Maker is a synonym of Creator, and I’ll stop here on this line, it will take to long to list all similarities.
-tricked by the voice of Mythal she was hearing after she started wearing that nice Horcrux of Mythal.
You know, this one. http://dragonage.wik...m/wiki/Andraste
That looks just like the crown Mythal is wearing since her retcon in Dragon Age 2, and I think I saw that crown somewhere else.
Oh yes, Meredith was wearing the same one during the last fight in DA2, and even before, can’t remember exactly.
What a coincidence that she was wearing the same crown years after Mythal arrived in Kirkwall on ‘business’.
Another coincidence is that both Meredith and Andraste thought they were hearing/doing the Maker’s work while wearing it.
And the biggest coincidence of them all: the actions of both Andraste and Meredith ended up in a holly war against mages, followed by the death of many and the complete enslavement of the rest.
But no, the biggest coincidence is this: the temple that housed the ashes of Andraste, the Bride of the Maker was build on top of an older temple dedicated to Mythal, the wife/mate/life partner of the first Creator, and one of the Creators in her own right.
Just a set of many unrelated coincidences, I’m sure.
-tricked by the voices of Dumat/Elgar’nan and Mythal combined. The last two theories are not mutually exclusive, they even make a better combined one.
1. Mythal has someone perform the famed ritual the year Dumat was killed.
2. Same year, Andraste is born.
3. She can hear voices from a deity called the Maker, blab la bla.
4. After a while, she begins to spend a lot of time in meditation, an act that is followed by any Seeker recruit, which can make possession very hard.
5. Seeing that Andraste has doubts about the voices she is hearing and fearing that she will discover the existence of the other soul inside her, Mythal gives her a part fo her soul as well, to make Andraste ever more umbalanced.
6. Since then, she also claims that she is also the Bride of the Maker, and we know that Mythal and Elgar’nan were to the elven pantheon the same as Zeus and Hera were to the greek one.
6. Also, Andraste contacted a disease at an early age that made it impossible for her to have children. Then, out of the sudden, after she wears the Mythal crown(Mythal being the godess of motherhood and justice and love and whatever), she can procreate again, having several daughters that leave her side before her end.
7. Here my crackpot theory goes off the reservation. Since Andraste was born in Ferelden, maybe her daughters chose to hide there. And maybe some of the descendants of those daughters were vessels for the other god souls. And maybe some of those descendants were named Flemeth, Morrigan, Yavana, etc. That would be an awesome twist if it were true, since ‘Flemeth’ would theoretically be Morrigan’s ‘mother’, or at least her ancestor.
-ooor maybe Andraste was just insane. Just saying.
The final point is this: the Circle might be built on a lie.
The Circle is treating the mages as slaves(check any definition of the word you want and you’ll find that it matches the situation the mages are in to a T, and in some cases is even worse, because slavery is also accompanied by torture, in it’s many forms).
The Circle doesn’t work, because even after centuries of existence, the magic is still a problem, and nobody is trying to fix the issue, namely the danger of possession, and settle for just limiting the end results. Because greed. And laziness. And a world with happy mages(or at least mages who make sane/logical decisions) would be a boring one for a video game.
But since the templar side has better characters and a cooler quest line, death and slavery to all mages.
But I think I should also add a line on topic. Mages. All the way. Every single time. Except that one time, but only for curiosity and didn’t even continued long after the breach sealing with templar help.
I like magic and hate drug addicts. Sue me.