The sad part? The Imperium actually calls itself (canonically) the Dark Imperium. Both because of the lose-ish of the Emperor and because they are painfully aware of what they have become and the crimes they commit. The worst thing of all, though, is that they are RIGHT. That every crime (ok, not all, but the vast majority of them) is absolutely necessary. Horrific, devastating, disturbing, but necessary. If the Emperor was still there it would not be. Both because of all the factions working together properly, and because of much greater technology. Hell, canon says that, during the Great Crusade, many Imperial Army regiments were equiped with advanced powered armor (like the mjolnir armor from Halo) and energy weapons that were so old and so advanced that they have no name.