When DA2 came out for many people including myself the Qunari were the saving grace in that game. The most interesting and unique group I have ever experienced. There were almost "alien" in their ways, but very understandable. The way and things lines were delivered...amazing.
They operate on insane troll logic. Their very notion of identity is defined through liberal application of the No True Scotsman fallacy. You can't say that you understood their views on identity and take issue with their mental gymnastics when it comes to gender. They're the same thing.
Let's turn right back to the Arishok talking about Tal-Vasoth. He says that he lost no "Qunari" to talk the Tal-Vasoth. This only works if you tautologically define a Qunari as "someone who would not become a Tal-Vasoth". It is the same kind of logical black hole Sten puts forward in DA:O. Applying this to gender, here is what Sten (and the Arishok) say:
Sten says: IF AND ONLY IF "Warrior", THEN "Man". One implication of the biconditional being IF NOT Man, THEN NOT "Warrior". We have no idea what Sten considers to be a warrior beyond the fact that it seems to involve "war" being your calling in some important way (not just a propensity for fighting). When you talk to Sten about the GWs, he views their "role" as being to combat the blight. In some sense, that's a "Warrior" role. And then his mind breaks, because he has the fundamental Qun biconditional about gender and warriors applicable in this case ("IF Warrior, THEN Man") along with your clearly defined role ("PC = Grey Warden = Warrior") and the implication of that biconditional ("IF NOT Man, then NOT Warrior"). So now Sten has to deal with you - by his internal logic - being in the "NOT Warrior" box but at the same time having you assert you are a "Warrior". That breaks his mind. Since he accepts his precondition can't be wrong - he's a good Qunari - he assumes you're lying and attempts to get you to relent (by saying you're a "NOT Warrior"). The Ben-Hassarath solve this issue by saying you're not "NOT Man". And that's the No True Scotsman fallacy.
This works the same way with the Arishok and Tal-Vasoth, since the logic there is just "IF AND ONLY IF Tal-Vasoth, THEN NOT Qunari".
Understanding this in terms of formal logic is very important, because as far as we can tell the Qun is content neutral. "Man" means whatever thing they define it to mean, not whatever it corresponds to IRL. People think the words the Qun uses about roles apprehend IRL meaning instead of whatever meaning the Qunari define those words to mean, which they often pull out of the air when confronted by a circumstance that doesn't fit their predefined notion. That's the Qunari's whole stick - the No True Scotsman fallacy.