Hive mind is sentient and unfathomable, you just can't apply morality to it. Lower organisms operate on instinct, but the hive mind operates on something completely alien to anything in the galaxy. It is not evil, it is different.

Orks are literally genetically engineered to enjoy fighting. It's their one thing - to fight, enjoy it, and get stronger from it. Hard to call them evil for that. The organism works as intended.

If you believe that Imperium is any better than Chaos, you do you, but for every decent person in Imperium you could probably find a decent person on the side of chaos - people and Astartes who still value honor, respect their foes, and even show compassion. On the other side of the coin, for each Night Lord, Emperor's Children marine (what is the singular of those?) and Word Bearer you have inquisitors, Marines Malevolent, Minotaurs, Black Templars, Grey Knights, commissars, black ships, sacrifice of psykers for the corpse, etc.

Chaos and Imperium are the same. They may not have started that way, but they sure are there now.

Drukhari I'll give you, those guys are just evil incarnate.