The Chantry creates most of the problems it then has to step in and solve- which helpfully allows it to consolidate and enforce its own power. There is no such incentive for the Dalish, so I have to conclude this practice is due to corruption from them having been influenced by an Andrastian mentality, which makes them no better than the city elves, just more hypocritical.
I highly doubt you actually believe the Dalish of all people were corrupted by Andrastians. If they take on this practice, it's by their own accord, and you can blame them for it, whether it is corruption, or if it's that they too recognize the dangers a mage is born attracting from birth.
I've seen enough zombie movies to know how people react to situations like this, lol. That's a joke, btw, I know it's not the same.
I can admit that the majority of people in Thedas probably overreact to the issue, chantry certainly and Dalish included. Now others need to admit that when you look at it, you really can't blame them, given the very real dangers a mage posses simply by existing. That isn't something easily dealt with, no matter what camp you stand in. If I told you to open a door out of 10, and one of them had a monster behind it, how safe would you feel?
edit: Actually, the door would just open on it's own... I'd get the hell out of there or torch the place.