Personally I saw Dorian's quest as being a lot less about Dorian being gay and his father's views of that than it is about his father's utter betrayal of everything he taught Dorian. Namely, using blood magic to control someone for his own gain. I don't recall Elder Pavus making any blatantly homophobic remarks. Rather, he was rather dismissive of Dorian, seeing all of this as youthful rebellion and selfishness rather than Dorian embracing his sexuality or not wanting to conform to Tevinter. He reminds me of the sort of pompous elitist father figures who are just scandalized that their children are talking to the peasantry or doing anything remotely 'improper'. Meanwhile Dorian has to deal with his hero figure who taught him how to stand against the tide in Tevinter turning his back on his own ideals, with the added nastiness of doing it to change Dorian himself because he didn't fit into his role like Pavus wanted.
Now, the parent dismissing the kid's sexuality as just a phase or them trying to rebel for the sake of rebelling, now that draws on a lot of people's experience, unfortunately, especially in the LGBT community.
For everyone griping about how unrealistic this is, well...
Tevinter is based off the Roman Republic, not Medieval Europe, and Tevinter is still its own thing with its own prejudices. Sexual politics in Rome was quite different than sexual politics in 1100 Paris.
And the Pavus family does suffer for Dorian's choices. The thing here is, this individual Magister (can, depending on player influence) choose to accept Dorian's choices, and gives him his seat in the Magisterium. While Dorian not marrying a woman and not having children may befuddle or amuse other people in Tevinter, they're not going to take away his citizenship card. That danger is from the head of his family, and the removal of that danger is what happens in the quest.
It's not the great bulk of the Magisterium deciding that they should put their little eugenics program on hold. It's not Bioware shoving the gay agenda down people's throats. It's Dorian and his father coming to terms and putting up with the crap that comes their way. The whole bloody history of sexuality and politics and nobility is not monolithic, incidents like this have occurred before.
So that's just my view. 