I would not say the chantry is Evil, So much as its origional concept has been bastardized over the centuries after Andraste, with different people in positions of power manipulating the system for their owwn gain, or to more readily agree with their personal ideals.
On paper the chantry sounds like a good thing. "Light to all corner's of the world, united under one faith: to he who made the world and all of us so he will return and bathe us in light" from alot of outside thoughts from the chantry they would hear that as: "A fire to spread accross the world, purging those that would oppose the maker's faithful" better known as "Do what i say or i will hurt you".
and as most world spanning organizations the Chantry is not exempt from corruption, and degredation of its tennants, and minor changes to those tennants over the years and centuries they where written down.
"Magic is to Serve man, not rule over him" Basically no mage should rule any nation, this is a pretty basic creed that players hear from priests of the chantry now and again. Bastardized beyond belief, as seen with the tevinter imperium. this flows into the Other quotes regarding Apostates, Malificarum, and Abominations. - Magic Is Bloody Dangerous if you dont know what your doing! as such the Circles of Magi where formed to teach these people how to control their gifts. but some where along the lines, someone had a bit of a caniption about having people with the power to light cities onfire with their mind, and letting them walk around like regular people. ergo, the Mages get locked up in their towers, with their "scary anti magic sponges" (Templars), and we start to see animosity.
the Templars are the Guardians of The Mages, where that got bastardized into the Wardens of their Prisons i dont know honestly. Their apart of the Harrowing to protect the mages who well.. blunty put "Suck at their Job", and Slay the Abominations. Yes there are alot of Anti Mage Templars out there, But there are also good Templars out there that side with the Mages Like Ser Gregoir, and Rhys's lover in the Novels.
The Chantry Enforces the laws that will keep people safe, and away from the bad things in the world. i believe it was said in the Party Banter forums Best: "Maybe the Maker's Job is Done" he was the Creator of the World, and People, and All Things, maybe somethings werent ment for Humans in the Dragon Age Universe, Ergo the Laws. Maybe the Black City where the Maker Resided was not ment for "US" and as such the Maker saw the Invasion of this City as a Sign Mankind is not ready for this power. and he Unleashed the Darkspawn to remind Humanity: "this is Your fault for being Impatient, and unwilling to slowly gain things that you dont yet understand". But Humanities Chance to learn what they didnt know, died with Arlathan home of the Elves, because Humans where Impatient and did not want to share Power and Knowledge. and Becuase of this decision by the Maker Dwarves lost their Empire. Smooth move Humanity.
I Cannot Say wether or Not the Chantry is "Evil" because infact it is not, it is Merely Corrupted due to Political and Morale changes with each Ranking member of its Hierarchy, if a person doesnt like a certain rule, their going to change it to benefit them, and that causes Seperations As seen with the Tevinter Chantry, and the Andrastian Chantry. Most of the Nations see Slavery as Wrong. the Tevinters do not, and as such it is probably not religiously Taboo'd about slavery. (We dont really know much about the Tevinter Chantry as a whole).
The Chantry is not here to tell us "Do This, Do That, Do it This way as well" No, the people that believe that are Fanatics, and Deserve to be Stepped on and ruled over because their to dumb, to read between the lines. Most people would see the tennants of the Chant of light, as Ambiguous Guidelines.
"What out for Signs of Taint, The Man is a Mage, show caution"
"All Beings are Equal in the Makers Eyes, No one is better than anyone simply due to race"
"Evil is Bad, Plain and Simple, Unite and Smack that mother Down"
"Tis the Hubris of Man -" yada yada yada, we all know the quote. "Man is a Fickle Creature, and always want more... Moderation, if you want something bad enough your willing to cheat, you probably should not have it"
((Onto the Topic that has come about while i wrote this, see above quotes about Humanity screwing the world over. You Recognize this Person as the Maker, your Creator, your all mighty Father figure, when you die, you go to his side. so... Why the Hell Would you rush to the land of the dead, just to try and kill him and take his power if he can re-make you at will? kind of a no brainer.))
As such, NO the Chantry is not evil, merely misguided, and set itself up for the massive fall we are seeing in the mage/templar war, and will see further in Inquisition.