Texas Joker 52 said:
You're both right and wrong.
Right about iom being xenophobic assholes. But if you knew more about 40k you'd know it's for good reason. Before the current iom man did go through a star trek phase where it tried to be all buddy buddy with aliens. You know what happened?
At first sign of weakness aliens overran, conquered and enslaved the humans when they became isolated from each other due to catastrophic events making far flung travel and communications impossible.
That is the short story of what motivated the emperor's crusade that ultimately made humans the dominant power in 40k to the point they can be compared to the roman empire in that they achieved maximum expansion and subjugated all.
That said... Iom/xenos relations are complicated, eldar and iom are friendly on occasion and there's a friggin craftworld in the sol system (why iom hasn't blown it apart yet is anyones guess, you'd think they would do so out of fear at the very least) and the jokaero are one of the xenos races deemed acceptable by the iom as they present little threat to humans and can supply them with unique tech.
As for tau... Don't be deluded, they ain't as nice as you think.
That whole "for the greater good" is a facade and tau society is somewhat of an orwellian nightmare, especially if you're a human where you'll always be a second class citizen no matter what the propaganda tells you (lol all valude equally. Yeh you're definitly valued as meatshield for the tau firewarriors ^^), but worst of all, you'll be subtly brainwashed and conditioned to serve and die for your grey skinned masters who look down upon you for being a filthy gue'va.
And i'm not even going to bring up the tau ending of dark crusade where they sterilize humans (without telling them of course) so as to discreetly eliminate the humans they promised they "liberated".
Tau come with smiles and a dagger behind their back, they are worst then eldar in this regard (for them, eldar lives>any amount of human lives, they don't pretend otherwise).