Varian only attacked thrall and sylvanas in undercity after he saw human skeletons and innocents being a play-tool for the forsaken.
I think an alliance leader actually caring about his country seems weird to some people. All they talk about is how there must be a unity to fight some bigger threats.
But if alliance lets everyone walk over them every time for some false unity, there won't be any alliance left to fight those bigger threats.
Since the start all of varian's actions have been about defending the alliance. I don't see anything to hate about him.