While likely this man's idea of liberty for mages coincides with our apostate characters, perhaps your characters should realize it's the way it's being going about they can't agree with. It's a method that will only garner more hate and fear from the people of thedas, eventuall until everyone who is not a mage will seek out to kill every mage.
in the end, it would become a holocaust, but for mages instead of jews. Trying to avoid such a fate, they join only on the reason that they want mages to earn their freedom without that threat.