If I don’t get along with my neighbors trust me my first thought will never be to muerder them.
I’ve said multiple times that I hated Garithos and in that case it was about would have struck first and Sylvanas won that duel.
But to go from that to actively torture, experiment and kill is a whole other league.
At the end of the day I’ve always defended the idea of Forsaken staying in Lordaeron because it’s their rightful land but they chose not to live in peace. They went on to inflict misery on others and expand their decay as much as possible.
Even Varian helped (although reluctantly) Sylvanas retake Lordaeron but what triggered him to declare open war on her? the sight of all the vile things they’ve been doing under her command.
She could have easilly prepared for war, built defenses and make alliances with the Horde for her protection and by doing that they would be the good guys making Stormwind the evil faction but the Forsaken became the bad guys right from the start.
Hopefully Calia can turn them into good people if that’s even possible.
*P.D. I don’t like Calia as the leader of the Forsaken so Blizzard needs someway to build her up like super fast for things to work out.