Seriously, their society sounds so overtly positive in the face of a preposterously hopeless and uncaring universe, there’s no way even the codex is telling the truth.
It’s like being stuck in a malfunctioning elevator with the Adoring Fan from Oblivion, or trapped in a burning home with Ned Flanders; the overt positivity just seems like it’s projection and there is a hidden darkness element somewhere waiting to come out.
The “Greater Good” religion simply sounds too good to be true. So they should all be destroyed, and their societies wiped from existence.
Edit: it looks like many people here don’t understand the obvious hypocritical irony and sarcasm written here…
Counterpoint: Tau were added well after GW had largely stopped with the topical political references, and were strongly unironically positive in their earliest appearances. The addition of gets-hot railrifles was a notably darker element in Tau at the time and was still lighter than the IoM.
Darker elements have been added, but the faction functioned without that element in their original form which has changed far less than other factions’ (due to the relative newness of the faction) so it’s not core to the faction’s identity.
Additionally, virtually all of the early dark elements in the Tau were either commonplace in the IoM or significant improvements over the IoM’s status quo. Through your suggested lens, this would have some interesting implications.