The difference is, Mages never had access to green fire or the spells it affects.
The classes that originally could loot and wield the Warglaives of Azzinoth are being disbarred with illogical reasoning.
To top it off the achievement for unlocking it is not exclusive to Demon Hunters, any class even the non-eligible wielders of the Warglaives can earn this achievement.
“I don’t like the way it looks on others” isn’t a good reason, it’s personal bias, it’s an excuse.