Eh. Well, the Tau in the game seemed friendly and well adjusted at first. Then I beat Chaos and hit the line about "Some Kroot ate dead chaos marines, and just in case that was going to somehow corrupt the entire Kroot species, we rounded them all up and had them shot." That got me feeling all was not well in Greater Good land. Then the ending and the 're-education camps' and I realized the greater good was a polite euphamism for Tau domination. Space commies.
The guard...well, I can't blame em for being psycho religious, not when gods and demons walking around are part of their everyday life. They came across as complete xenogenocidal maniacs though, which is points against them even though most of the other alien races seem to deserve it.
Are the other major races not shown in Dark Crusade? I've heard of the Tyranids, which are apparently what the zerg were stolen from, so I'm guessing they're the 'eat everything!!!!!!' types, not exactly bastions of morality.