Yeah this is the thing I like about Elder Scrolls lore. There aren't clear good guys or bad guys, there's a good amount of nuance and perspective as to who is "right" based on their allegiance.

Does the Sixth House do reprehensible things? Yeah. But Dagoth Ur shone the truth behind the Tribunal's actions which are implied to be true in the lore (Ashlander texts), and thus isn't the evil Boogeyman that Vivec makes him out to be.

Edit: meant to be a reply to HotSoda's comment but somehow got posted to the main thread.