It is more relevant to the time of Skyrim, but even by the the time of ESO, roughly 700 years earlier, the Elves didn't want to try and kill or enslave all Humans. Same goes for current AD, they're actually more racist than the AD in ESO, but they still only wish to overthrow Human rule, not destroy the Human races.
So just to be clear, which Dominion is the latest/current one? My understanding is that it's the Skyrim one. So by ESO, the Elves know man isn't going anywhere, so they just continue their human/Talos hating bent the next 700 years (barely two generations for them, right?) and that's the Thalmor we see in Skyrim.
No, that wasn't their purpose. The Thalmor of that era wasn't an ideological group. It was simply the name of the combined Altmer-Bosmer government, which came into being to prevent a Colovian take-over of Valenwood.
As as I understand it, the Thalmor as a political party didn't come into being until after the fall of the first Aldmeri Dominion, and then it was composed of Altmer and Bosmer who wanted to restore the Dominion. Over the intervening 1000 years they also took on the ideology we all know and love.
The Thalmor don't represent all Altmer or all Bosmer. They do represent the mer that really wanted the Aldmeri Dominion restored... the political entity utterly crushed by Tiber Septim. So you can say they are naturally biased to hate Talos by their geo-political goals.
You must also remember that the Altmer felt isolated and betrayed after the Oblivion Crisis - which did irreparable damage to their culture - because the human-led Empire was unable or unwilling to help them and they had to bear the devastation and loss of their Tower alone.
It wouldn't surprise me at all if there was a general sense among the Altmer, and especially among the Thalmor, that the Oblivion Crisis wouldn't have happened at all if they had been in charge and a strong desire to blame humanity for it.
In short, I don't see any need to force the supremacist attitude, it feels pretty reasonable and organic to me given recent (to the mer) events.