I've seen a lot of people that are confused or even angered by the event that have progressed in world of warcraft concerning some of the 'cannon' lore. Prince Kael'Thas Sunstrider for instance.

Generally Kael was a caring, if a bit arrogant, kind of guy. After the Scourge attacked his people he took charge and assumed command over the survivors. That, of course, was back when Quel'Thalas fell and the high elves renamed themselves blood elves.

This is the turning point for good old Kael. Undead hatred and a severe hatred for the alliance since he felt they had failed his people. Plus compiled onto that his people now had nothing to feed their addiction to magic since they had lost the sunwell.

After the sunwell incident he joined, reluctantly, with Warden Shadowsong and High Priestess Tyrande to hunt down illidan. In a long and conveluted process he ended up using the Naga for help twice which got him repremanded and then thrown into the dungeon of Dalaran, where he had spent a good portion of his life. Lady Vashj freed Kael'thas from the dungeons and helped him escape to outland where Illidan was waiting. Illidan convinced Kael that he could help with his peoples' addiction so