I've met you in these dreams. You're the good sort in a a terrible situation. But I've met good Templars and horrible ones, and but you wouldn't damn all Templars for the ones that do wrong, would you?
And it would depend on the danger, wouldn't it? How one could define what a dangerous mage is, because in the eyes of the Chantry anyone with magic is dangerous. They pose a threat even when they take a shit by themselves. For a mage that attacks someone out of the blue, and actively uses their power for violence against innocents? Yes, there should be punishment. The same would go for any berserk swordsman that started stabbing random civilians in the streets.
Some of us don't have a choice in what we get from these, but at the very least - being a Templar is a choice. I can assure you there isn't a need for an order to watch magic users around these parts.