*I'm cutting these quotes down considerably. Sorry about your day BTW Artemis.
I don't understand this. How is the approach to his character wrong? Does he not seem genuine to you? I find him a deeply complex and damaged character; it's why he is my favorite Dragon Age character. Fenris is not someone who can be easily "fixed"; I think he will always have these fears hovering over him. That said, he's a strong person; I think he will go on to live a healthy life, especially if my Hawke is around to help him out from time to time 
He is not a bad person; he cherishes the notion of freedom. He is conflicted when he sees the Gallows. It strikes him how much it still looks like a gallows. But by the end of his discussion with Hawke he basically squares his shoulders and says that it's necessary. He really believes this, even though a part of him detests holding people in cages like animals. Fear and his previous experiences make him a deeply conflicted character.
Again, no problem with his character per se. Just feel like the writers did a bad job arguing the other side (of the mage issue) through him, that's all.
Don't know if you played Mass Effect 3, but I'd liken him to the salarian dalatrass. Fenris is not quite as bad, but at times he reminds me of her in the wrong ways. The dalatrass was arguing for the other side of the genophage issue, and while she made some fair points, she mostly came across to people as spiteful and a bully. Fenris has his moments where he makes compelling cases against freeing mages, but they're buried underneath many instances where he comes across as vitriolic and passive-aggressive about it. And perhaps I've interpreted him to be hostile in cases where he actually isn't, but if I have, it's because he comes off that way from habitually acting like it. It leads one, in turn, to attribute his position more to his negative feelings and biases rather than any rational points he has to offer.
Basically, if he were on my debate team, I'd take him to task a bit on his tone and connotation.
Oh, I see. Well, I don't think the writers intend to make us choose one side or the other. When I'm watching Game of Thrones, I don't feel as if I'm supposed to pick who to support, the Stark's, the Lannister's, or the Targaryen's. I'm just enjoying an amazing show with well-written, nuanced characters. It's the same with Dragon Age. I don't support the mages or the templars. I'm just creating characters and playing in this amazing world and interacting with these great characters.
It's fine for a TV show, but this is a role-playing game where that particular issue is central to the game -- it even ends with you choosing a side. =\
I find Fenris pretty rational in the conversation you have with him when you bring him to the Gallows for the first time. He does not think mages are all evil or inherently bad persons. His only concern is that they're human (or elvhen, but whatever) and that means that most of them will cross a line (i.e., turn to blood magic) when pushed into a corner. It can be to save themselves, or someone they care about, or because they want power, or because they did not like what they got for dinner that evening. Doesn't matter. He thinks that every mage (meaning every man and woman) has a price. And honestly, I think he's right. How many people wouldn't do anything to save someone they love, even if it means doing something morally wrong? I know my Hawkes would not have hesitated to use blood magic if it could have saved their family. That's not evil, that's human. But it can still be dangerous.
You don't have to convince me of his position. I actually agree with it, for the most part.
Thing is, Fenris was initially one of the things in the game that detracted me from that position rather than getting me to understand it.
1. He thinks Thrask deserves to be blackmailed for being a hypocrite.
2. He believes all mages belong in the Circle.
3. He believes Keran could be possessed by a demon.
4. He believes all mages belong in the Circle.
Now, reasons:
1. Thrask kept the abilities of his daughter a secret and in the end she turned into an abomination. As a templar, he has a duty to protect others from mages running free and potentially causing harm. Apparently he has neglected this duty, and it would be better to expose this than protect Thrask.
2. Grace was the lover of a blood mage, hiding in a cave with more blood mages, who all attacked on sight. She could very well be a blood mage and lying about it to save her own hide. Oh, and guess what? Fenris was actually right! As can be seen in Act 3.
3. Merrill and Anders are not the most trustworthy sources as far he is concerned, and their methods to test Keran are not guaranteed to be fool-proof. Keran could still be posessed, or his mind altered by blood magic.
4. He outright tells you why. He thinks Emile is acting innocent and dumb to deceive you and let him go free. Might be true or not, we never get 100% certainty in this one. But even if he is not a blood mage, he should be in the Circle as far as Fenris is concerned. If he is actually as dumb as he acts, he can easily end up harming others in the end.
1.) And what good does blackmail do in response to an uncommitted/negligent Templar, aside from turning his misconduct into your profit? The problem-Templar remains free to continue violating his duty, and his superiors remain unaware of it. All you've done is make him feel like he might lose some coin over his mage sympathy if he's found out, and to be more careful in covering his tracks. He is not, however, confronted directly for not doing his job.
It comes off as really passive-aggressive for him to support it.
2.) Grace was an abomination come Act 3, which may well have come long after Act of Mercy has been completed, so I wouldn't call him "right" on that. In fact, if life in the Circle under the Templars is what pushed her over the edge, I would even argue that he was wrong!
3.) Does he actually have sound reason to believe their tests are flawed, other than the ad hominem at hand surrounding Anders/Merrill?
4.) See, that's kind of the whole problem I have with him in a nutshell. There are several, valid concerns one can raise in the scenario with Emile DuLauncet to support sending him back to the Circle. What you get from Fenris, however, is a far-fetched accusation that's utterly unconvincing.