Even before the zerg turned on the Xelnaga though, they still had those innate qualities of assimilation, conquest and evolution, even when they were still those little worm things. They were altering the bodies of their hosts well before they rebeled against the xelnaga, that in itself is aggressive behaviour and would likely continue on down the road.
Perhaps the fallen one made the overmind want to seek out the protoss specifically and destroy/assimilate them but even if he hadn't, the zerg would still want to evolve into the most formidable creatures in the universe and would fight the protoss when they made contact.
And now the issue with Kerrigan, well I do think the original game portrayed kerrigan as having been morally/ethically altered by her infestation. Like she is sending out telepathic messages of "help me!" and then Raynor comes to help her and suddenly she's like "fuck off." That seems like an alteration to me. But that doesn't make the queen of blades any less of a real character. I think that the queen of blades was kerrigan who was altered to be a bit more bloodthirsty and thats it.

