From the perspective of any Man race (Nord, Imperial, Breton, Redguard), the Thalmor are evil. Their goal is explicitly the extinction of all mankind. While the Empire has made a tentative truce with them to avoid being destroyed, pretty much every single person ever (aside from some vocal Stormcloak partisans who think the Empire has straight up swallowed the Kool-Aid) knows that it's only temporary and -nobody- likes the Thalmor.
An Altmer or Bosmer might side with them, or possibly a Dunmer (though it's doubtful, considering they have no power to back up any attempt to enter into the Dominion as equals instead of vassals), but any Beast Races who do so are fooling themselves. Mer generally don't have genocidal tendencies towards beastfolk that they do towards Man, but they do have a long and hallowed tradition of subsuming and enslaving them.
I wouldn't ever side with them even if I could, because the only thing worse than an arrogant Nazi is an arrogant Nazi elf.