Your definition of hero is too narrow is the problem.
If you wipe out The Absolute from a desire for vengeance on those that enslaved you then you improve the world. It doesn't matter that it was a bloody path or that a lot of extra people got killed that didn't need to. The world is improved and baldur's gate is saved.
Not that I disagree with the general net positive sentiment, but does that mean Stalin is a hero because he helped defeat Hitler, even if a lot of extra people got killed?
