That's an interesting reframing of what we know. We don't ultimately know much (and I'll note that it's Aaravos, who seems an unreliable narrator, who does the narration in S1E1), but the precipitating event we were given was that humans developed Dark Magic, which explicitly destroys magical life in order to power itself. We're told not that an ethnic cleansing occurred, but a forced exodus; which certainly has its own issues, but isn't 'ethnic cleansing'. We also have no knowledge of whether or not the 'terrorist dragon' was acting alone.The assassination attempts are way, way down the list of why the elves are jerks. Significantly higher is that the whole situation opened with the elves enacting a bonafide ethnic cleansing on the humans, then after that also proceeded to terrorize them with their allies (a dragon flying over a town repeatedly while not attacking is roughly equivalent to hovering an attack helicopter over one and pointing its guns at some civilian housing, but not actually shooting).