You know what really grinds my gears, though?
I went back to play DA:O, WK again just to make sure I was right.
The Grey Wardens didn't "invade" Ferelden under Sophia Dryden and Teagan should bloody well know it, especially if Alistair is his king.
Sophia Dryden was a legitimate cousin to the Theirins and in line for the Throne. Ardal Theirin ended up with it. Instead of executing Sophia, he made her join the Grey Wardens, effectively removing her from the succession. However, Ardal turned out to be a tyrant--the worst, apparently, until the Orlesian occupation that ended 70 years before the Fifth Blight. The end result was that the nobles of Ferelden--including Cousland, Guerrin and Wulff, started a Civil War against the Crown, citing abuses (any further details are "lost to time" but we do know that Cousland was executed by Theirin).
Wulff then sent a letter to Dryden begging for help against her cousin. She used the only force she had available to her--the Wardens. No one objected to that, except the framming Wardens at Weisshaupt. It went steadily downhill from there, Theirin won, Dryden used demons. Dogs and cats started living together--chaos.
Then the Wardens were exiled by Ardal Theirin for "getting involved in politics" but mostly because they'd stood against him. He then kept on with his tyranting and suchlike until his own death. No one liked him, including the other Ferelden nobles. He is, in fact, almost a byword to the nobles of Ferelden as a blip in the Theirin line, partly because he exiled the Wardens--who were considered, still, to be a noble and honourable Order if you paid attention at the start of DA:O. The only one who had "issues" with them was Loghain Mac Tir. And the "whys" of that is another thread.
In any case, Teagan never believed the Wardens did such a thing. His exact words to the HoF in Redcliffe. "I don't believe a word of it."
So, Teagan's not only unreasonably "against" the Grey Wardens, (especially if he has a crush on the HoF/she is his queen/Alistair is the king/Redcliffe was saved, etc etc), he's not even doing so for the correct historical reasons, and he's completely OOC to say so. (Whether the IQ should be disbanded--he had good reason to be concerned. The way it was handled? Very un-Teagan).
It's just bad writing. That's all.