Ughh, on my second playthrough and got this banter between Solas and Dorian I'd never heard before:
Dorian: Solas, for what it's worth, I'm sorry.
Dorian: The elven city of Arlathan sounds like a magical place, and for my ancestors to have destroyed it...
Solas: Dorian... hush.
Solas: Empires rise and fall. Arlathan was no more "innocent" than your own Tevinter in its time.
Solas: Your nostalgia for the ancient elves, however romanticized, is pointless.
Solas: If you wish to make amends for past transgressions, free the slaves of all races who live in Tevinter today.
Dorian: I... don't know that I can do that.
Solas: Then how sorry are you?
I'm sure this was posted already but... it's really interesting! It seems like a lot of people think Solas' ultimate intention is to free to elven gods, but from this banter it seems like the complete opposite, that he intends to leave them behind and start freeing slaves again... it's weird. The hints about what he intends to do go both ways! And chiding someone for nostalgia about ancient elves... c'mon Solas. 
People have called Solas something of a "race supremacist" for his comment "the People need me" in the post-credits scene. Like somehow his desire to undo his ancient mistake that might have given the elves their current lot means he wants to establish elves as the new world order, or wants to screw over or abandon other races to a terrible fate just to help elves.
I don't think that's entirely fair, based on this conversation with Dorian that you just shared and many others. Solas shows that he cares about helping people of all backgrounds. He approves of you helping human refugees in the Hinterlands as much as he does of you helping elves. He badgers Varric about how Orzammar could better use the resources they have to become a global power instead of a rotting city-kingdom, and asks how modern dwarves can just passively accept being a dwindling people instead of the great empire they once were. (Showing that he cares about the fall of the dwarves' greatness as much as the elves'.) He shows disdain for subjugation of any kind; cares about mages; tries to give Sera pointers on how the Friends of Red Jenny can topple the established order, and more. He makes it clear that he wants to help people, just elves just happen to be included among the groups of people he wants to help.
Unlike Sera, Solas doesn't seem feel that "people" and "elves" are mutually exclusive. That helping elves means you don't want to help other people, or that wanting to help "people" means you shouldn't care about elves. Solas' desire to help people includes elves, doesn't exclude them; and vice-versa. I think that wanting to help elves doesn't mean he doesn't care about other people; that wanting to create a new world that helps elves doesn't mean he wants to abandon or subjugate non-elves. The world he wants to make to help elves might also be a world he wants to benefit non-elves.
What people forget is that elves do get a raw deal in modern Thedas. Still largely enslaved in Tevinter and Antiva and other countries that allow slavery, and are disproportionately sold into slavery from countries that don't publicly allow it more than other races. City elves live as impoverished and powerless second-class citizens in non-slave societies, holding onto "a few traditions to distinguish themselves from humans," and Dalish live as "shadows wearing vallaslin" in forests. And all of this can arguably be traced back to whatever he did in the past that likely led to the sinking of Arlathan.
I think Solas does care about all people and wants to help all people enslaved or subjugated, but since the elves get the rawest deal, and that raw deal is a direct result of something he did in the past, he might feel more motivated to help them. That he feels more drastic measures are needed to help them because they are in the toughest spot and are getting the least help from others. (Mages at least have phenomenal cosmic power, members of every race, ties to nobility, and their own kingdom; dwarves at least have two city-kingdoms of their own and a hold on the lyrium trade that gives them leverage. Elves don't really have much.)