It's still really funny to me that they made the T'au basically be good but so insignificant on a galactic scale that they will never really matter that much, but the fact that one faction was pretty good instead of comically evil made the fans so mad that they decided they had to insert some plot point about how the whole society is mind controlled for nefarious reasons.

It would have been fine to leave it at "These guys can only be good because they dont face all the same galactic threats as the other factions" but that level of nuance is foreign to the average 40k fan.