Agreed, it made him look so stupid saying that stuff to the mage standing in front of you. Heck, even the Templar recurit Karen says something too that regards, as well. but I'll let him pass with that one. A lot of it sounds ignorant to me, since a fireball thrown by one mage can not light a city on fire, you would need about a dozen to do that, in the first place. He's a Templar he should know about, what mages can and can't do. I would have had him say that "The Chantry sees mages only as weapons to be locked away, but I see them as people that are not like you and me, and this is the reason I belive the Templar Order was created to protect the public from them, and also to protect them from themselves, when needed." This sounds more neutral than the "They aren't people crap."
I don't think he was in a neutral place at that point in time though. What he said suited his point of view as I am sure the events at kinloch were still rather fresh in his memory. I'm not one to make excuses for Cullen and the things he has said in the past but I do agree with him on some points. Mages are people yes, but they are not your average person. Cullen just chooses a very direct way of saying this instead dancing about it. They are dangerous, an untrained mage could jave the potential to destroy a village if they hit a pique from fear or anger or some other emotion and have no real control over their magic. But they are still people that need to be treated with dignity and respect. They deserve to be able to live a life free from fear just the same as non-mages and they are most certainly not a possession that can be used as a weapon and then locked back up when not needed. As for Cullen having the exact same lines for a mage Hawke, I think we can just put that down to lack of development time for the game as a whole.
"The Chantry sees mages only as weapons to be locked away, but I see them as people that are not like you and me, and this is the reason I belive the Templar Order was created to protect the public from them, and also to protect them from themselves, when needed." -- this is kind of where he is at in act 3 which is why I think Cullen has such great character development in the game for someone with such little screen time.