I love how, in any sane setting, the T'au would be The Villains, capital T capital V, but in 40k they're about the closest the setting gets to "good guys". They're an expansionist colonial empire that tries to force their ideology on everyone they meet and exterminates the people they deem incompatible with it, and somehow, because 40k is just that fucked up, they are one of the more reasonable factions in the galaxy.