I'd imagine that most people would simply see Dorian as stirring up drama of 'oh man, we shouldn't be doing this because I'm an evil Tevinter', but from my perspective that's a small part of it, a big part of it is romance anxiety.
With Dorian it's all bound up together. If you haven't, I do suggest you read his World of Thedas Vol. 2 entry.
I had a habit of self-deprecation just to lob some excuses of why we shouldn't be together as a defense mechanism against my fear of being a really bad romantic partner and fearing I'm getting something I don't deserve or shouldn't have.
Dorian does this as well. In this thread we've talked about how he occasionally tries to give the Inquisitor an 'out.' It's obvious what he wants, and that he cares, but he presents this flippant attitude because he doesn't expect it to last, because he previously had no grounds for such an expectation.
Because same-sex relationships aren't an actual thing for one to aspire to in Tevinter, it's not something he really ever considered as a factor in his life. His future has been planned to the last detail since before he was born. Even if he had gone along with getting married and just had his guys on the side, kept it a matter of pleasure only, he wouldn't have been able to have the kind of relationship that he wants with another man in Tevinter. Dorian is a passionate guy and is the type to want to be himself completely, saying to the world, "This is who I am. This is who I want to be with." He would not have been able to be open in Tevinter. David Gaider said of Halward that his issue wasn't with Dorian's "homosexuality in and of itself," and that he would have had no problem with it had Dorian "agreed to marry as intended, and kept his homosexuality as a private conceit." But that's not who Dorian is as a person.
In the Dragon Age setting, and Thedas at large, same-sex relationships (being together as a couple, outside of sex) aren't really a big deal, even for nobility. Considering that one does one's 'duty' to their family, has the correct marriage and produces offspring to continue the line, they don't really care. In Orlais for example, one can be openly homosexual and have a known same-sex paramour -- at the Winter Palace one of the male party goers is introduced along with his wife and a male paramour.
So I think the root of his problems lie in Tevinter. If he had been born elsewhere he might not have had the same issues. If Dorian were, say, Orlesian, and his father still insisted on him getting married, the differing views on homosexuality in Orlais might have made a difference for him.
Finally, romance aside, I think being away from Tevinter has been good for him. Being around different types of people, who think in different ways, around whom he has been able to be himself, can only have had a positive affect.
(Don't mind my long-winded posts... I tend to get carried away when talking about this character. I've given a lot of thought to his reasoning and thought process.)
We have Granny Smith apples in the US
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