Or it's indicitive of the Sabrae clan being unusually tolerant. The one in TME certainly wasn't.
We also had Velanna's clan respond positively to seeing Velanna in the company of humans, and Marren was willing to take the word of a non-Dalish that Velanna had changed for the better; we also have Ariane's clan, who welcomed an elven Circle mage into the clan. I'm not seeing how the behavior of Clan Virnehn represents most Dalish, given what we've read from their historian and what their hahren have said about Dalish and city elves coming together in an independent kingdom where elves rule themselves. There's also the issue of Thelhen using magic that involves spirits, despite how WoT reads, "Unlike other spellcasters, Dalish mages do not use any magic involving spirits, as they believe all spirits are dangerous." (page 104)
Given what we've seen from "The Masked Empire", Clan Virnehn looks like an atypical clan.
The overall impression I've gotten about the Dalish is they at best pity the city elves and at worst hold them in contempt for bowing to human masters. In either case, tehy don't consider them "true elves" thus the flat-ears epithet.
We are the Dalish: keepers of the lost lore, walkers of the lonely path. We are the last of the Elvhenan, and never again shall we submit.
Some of the Dalish consider the city elves to be culturally human, but we have some city elves who also use the term in reference to elves who leave the Alienage, viewing them as "flat ears". According to hahren Sarethia of the Highever Alienage, "Here, we're among family. We look out for each other. Here, we do what we can to remember the old ways. The flat-ears who have gone out there, they're stuck. They'll never be human, and they've gone and thrown away being elven, too. So where does that leave them? Nowhere." We also have some city elves look down on the Dalish as savages.
In contrast, we also have Dalish who don't share those views, like Merrill, who talks about the Kirkwall elves as elves, and voices that their plight matters. I think it would be a mistake to confuse the view held by some with the mindset held by most or all of them.