What caused the Alliance humans to hate the Forsaken?

[Zerde-sargeras (Zerde)]

So... did they just retcon every act of "Morally Grey" or "Evil" Alliance has done since MoP?

According to wowhead’s new article, these changes to the lore are in Chronicle 4: The Sunreavers are now stated to be directly responsible for the theft of the Divine Bell, meaning there’s zero doubts Jaina was justified in the Purge, given her warning to Aethas prior to the incident. Rastakhan pledged his fleet to the Horde right after G’huun died, meaning the attack on Dazar’alor and his death is a valid act of war. Also, apparently Genn was no longer involved in it, and it was just Jaina? A…

Maybe check outside the story forum bubble every so often. Regardless, the Alliance getting a pretty clean record.