So I finished Tresspasser again, for the...fourth time? Wow. I have played Trespasser more times then the game itself. But it is worth pointing out that Bull in the scene he betrays you says that the Vidisaala invited him there. Meaning, they were in communication, meaning Iron Bull had a lot of time to discover if it was a rogue operation. It wasn't a rogue operation.
No, she contacted him at the last minute via her viddathari agents just as the Inquisitor arrives at the Darvaarad. He wasn't able to verify anything with his superiors the whole game. Josephine's letter confirms that.
Also, Weekes and Epler confirmed that Viddasala was unauthorized.
... So because he's terrified to become Tal-Vashoth he'll follow a Tal-Vashoth... which will effectively make him a Tal-Vashoth
Because he's terrified to become Tal-Vashoth, he'll blindly obey the order of a Viddasala who might be Tal-Vashoth or might not be, rather than risk being declared Tal-Vashoth for not following the order.
Hissrad probably felt that it wasn't his place to decide that Viddasala was Tal-Vashoth, but even if she was, that would put her at fault, not him or any of the other Qunari who were being misused by her.
Basically, Hissrad was going the "safe" route, because he would rather be a dead Qunari than risk being labeled Tal-Vashoth, and it wasn't his place to think about the legitimacy of the order given to him. It wasn't his place to think about if the Viddasala was acting outside the Qun or not, of if she was authorized or rogue.
Yes, Iron Bull who knows fully well that the leader of a group of True Qunari not-rogues is a Tal-Vashoth,
Does he know that? Or does he feel it is his place not to think, only to do?
will blindly follow the order of a Tal-Vashoth in order to not be branded a Tal-Vashoth by the True Qunari.
Yes, that is what blindly following is all about. If he follows her order, at worst it only puts him in the same boat as the rest of the true Qunari who are following her orders. If he disobeys her order, at worst it makes him Tal-Vashoth, at best it makes him a real Qunari knowingly killing other real Qunari.
Not the True Qunari who tried to start a war, but the other True Qunari.
No, he may have feared this branding from the Qunari he was fighting against, or the Triumvirate, or even Viddasala. The branding could come from anywhere, and he wanted to avoid it by simply following the order. Even if Viddasala was definitely Tal-Vashoth (which Hissrad didn't know for sure because he didn't think it through), she could still call Hissrad a Tal-Vashoth and the real Qunari at the Darvaarad would believe her. This might then have implications among the real Qunari back in Qunadar.
Personally, I think Hissrad could have wiggled out of it by saying that his order to remain a spy comes from a higher authority than the "Dangerous Purpose" branch's Viddasala. But Weekes wanted Hissrad to turn on you. So that's how the story went. Hissrad blindly followed an order rather than used his mind to think.
The argument is nonsense, but it does have some nuance. Dai Grepher clearly contemplates there is some separate authority in the Qun that has the authority to declare someone Tal-vasoth. Not just any Qunari can declare another Qunari Tal-vasoth.
Thanks for catching the nuance at least. Hissrad can't just decide that Viddasala is Tal-Vashoth, especially since she is of a higher rank. Well, he could, but it would have no authoritative weight behind it.
All of this is to say that the only way he could be wrong is if somehow the IB was raised from birth to me a member of some secret police whose sole role was to identify and expunge dissenting from the Qun. But that's absurd - it would require the IB to be a member of the Ben-Hassrath!
But we know for a fact that Hissrad wasn't raised from birth to do spot dissenters within the Qun. He was raised to be a fighter against Tal-Vashoth and Vints, as well as be a spy in foreign lands.