Here's a question last night's discussion raised for me:

do you consider ANY of the factions in 40k to be 'good'? Not 'by their own standards' or 'well, in the context of the grimdark', but unambiguously morally sound.

My personal take has always been a flat no. They're all reprehensible on some level. Each of them could even be said to mock a certain kind of self-righteous evil from a satirical point of view.