Theres a great history about mage imprisonment. Go and read the wiki.
There's even greater history about templars and the Cantry as a whole being swines not only to the mages, so maybe you should educate yourself first. But it won't help the issue, of course.
In some ways the Dalish are no better then the Tevinter.
Among the Dalish the mages are the ruling class and the Keeper word is law unless they turn to blood magic.
Horrible, horrible elves. How can they let a mage rule over them.
Omg, we should do something, they're totally not right. Like, they haven't been dealing with such things for many-many years now. Savages, what's there to say.
The problem with Tevinter is not that it ruled by mages, but that it ruled by nobles who happens to be mages. There's a little difference between Tevinter and Orlais, they both have vital flaws but the root is always the same. And it's not freaking magic.
At any rate as far as I know there is not a single society in Thedas where mages doesn't rule yet live side by side in peace with the rest.
Nevarra and Rivain dissaproves.