Wrong. The Protoss position is one of racial superiority above humans and the belief that Terran sovereignty is secondary to stopping the spread of Zerg. Unilaterally wiping out human settlements without any attempt to reach out to Terran authorities first reflects that elitist Protoss position.
Tassadar is an isolated outlier and considered a renegade and a traitor, not for siding with humanity, for simply not wiping out large numbers of Terrans as instructed by Protoss high command. Tassadar and his handful of buddies do not represent the Protoss culture or policy. And maintaining large galactic fleets that routinely wipe out rival races to stop a third party race from expanding doesn’t sound like non intervention. Terrans and Earth humans are all HUMANS.
And, compared to the alien races, they have more a vested interest in human survival and human power existing in Koprulu as opposed to alien supremacy (and human extinction) in the region. UED are jerks but they are at least human jerks and can be relied on to put humans first (colonial sovereignty is not equal to human survival necessarily and in the face of powerful alien threats, sovereignty and ethical issues are really secondary).
Who says the Protoss weren’t imperialists? Huge fleet flying around interfering in the affairs of other races, the attitude of racial superiority, martial culture, Protoss high command ruthless attitude toward human life.
Who says they aren’t trying to call the shots in Koprulu? When things don’t go their way, they call down alien hellfire from their carriers on innocent Terrans and thats OFFICIAL Protoss policy. Kerrigan didn’t leave Terrans alone, she helped the Overmind against humanity then, when the UED whooped her, lied to get humans on her side, then resumed hostilies against humans again in her quest for power, slaughtered the human UED fleet to the last man and let Mengsk survive as a mere sadistic gesture to let him suffer and because she knew he could do nothing in his current state to stop her inevitable victory. How is that a great situation for Terran humanity?
They’re worse off than if they had allied with the UED and at least made the galaxy safe for humanity. If all factions are jerks who wipe out each other routinely, at least the UED are human jerks. The Protoss knew the nature of the Zerg as single minded and all consuming, sacrificed Terran lives to stop the Zerg even, but then ally with the Zerg to stop the human UED? You need to have a lot of contempt for humans calling the shots to side with the Zerg against the UED. The Terrans have seen the threat of the Zerg, yet hate the UED more because of sovereignty and purification policy issues, when the latter will still result in a better deal for the Terrans than outright destruction by the Zerg.
Kerrigan didn’t stop doing anything, she had beaten everyone into submission and could now afford to relax before resuming her standard Zerg agend she’d be pursuing from the beginning.
One could make the argument that the UED would calm down once they had neutralized all threats, too. Again, a UED alliance is a better bet for Terran humans in terms of what matters: human survival and power in the galaxy, the UED is not uniquely bad compared to other factions given that other factions are fairly similar in terms of tactics and goals in some sense (UED purification policy is not as bad as extermination by the Zerg, sorry buddy).
If this were just a story of the Terrans vs UED in a struggle of sovereignty like American Revolution in space, we could debate ethics and such. This is a story of racial struggle between humans and aliens (in which the aliens have drawn first blood and are bent on human destruction or domination of humans).
Quibbling over the distasteful nature of the UED is really not important considering the stakes here. They’re the only hope that humanity has at existing and the alliance of Terrans with two rival alien races against a fellow human faction (within the context of racial struggle in the galaxy) is simply confounding.
The Protoss to some extent are guilty of this with their insistence that they engage in hair splitting over the Dark Templar rather than unite against the Zerg, and sure enough, they suffer for it, yet they don’t learn the lesson, still side with Kerrigan (who has a terrible track record and is only friendly because she needs them temporarily) because “the UED does eugenics”. But the Zerg killing everything? Nice! lol.
The Protoss exert their authority using their fleets, murder Terran settlements, purge their own society of perceived undesireables and regard humans are inferior and expendable. The Zerg are just murderous monsters from day 1. And people think an alliance with them is preferable to the UED? How are they any better? None are angels, but the UED are “bad”. OK guys!