Well Cullen is an Adviser, it's not really his job to go off on one. There are plenty of characters who can be disrespectful towards you and your views if you irritate them enough. Some of them don't even need that Solas will be immediately hostile towards your character if you are Dalish and some of the things he says to and about Sera are kind of awful. Blackwall can be incredibly judgmental to the inquisitor (which is incredibly hypocritical in his case), Dorian is very arrogant, he just talks down to you in a much nicer way.
It does address one example where some people get along with a character who doesn't share their character's point of view, however, which was brought up earlier in the thread where some people felt the Circle was the pressing issue that caused some people to dislike her. I also played as a Dalish character, and I got along with Solas because I was actually allowed to disagree with him, and because he was willing to hear me out instead of talking over me.
Frankly, I didn't have this issue with Blackwall or Dorian. Blackwall was pretty humble about the fact that the Inquisitor turned out to be an elf, and promptly apologized that the thought even came to mind. He also listened when Lavellan told him that he wasn't the Herald. Dorian is certainly sarcastic, but he promptly agreed when my Dalish mage told him he could keep up. He also lets his guard down in the scene with his father, and it comes across like he's putting up a wall due to what happened when his father discovered he was gay. I'm sure your mileage may vary, but the characters and interactions are simply different than the ones with Vivienne.
Also, considering what Sera says about the elves, it's understandable why Solas would have an issue with her. I don't hate Sera's character, but I do take issue with some of the things she says.
Sure Vivienne is more petty and it's easier for her to dislike you but she doesn't require you to make all the decisions she would make, you can get a lot of approval from her even if you disagree with her if you pick certain dialogue options.
Sure, but her general attitude and her stunts are going to make some people dislike her, as well as the writer's choice to prevent people from disagreeing with her. Even Iron Bull and Blackwall (in some dialogues) are basically prohibited from taking her to task.
and again I am still not sure what you are referring to when it comes to her pretending to know more about the dalish/vashoth. if it's what I think it is then I am pretty sure you are making a mountain out of a molehill.
The dialogues where the Dalish or Vashoth can talk with her about their magic and culture.
You're certainly entitled to your own opinion about Vivienne and these scenes, of course. Everyone is going to have their own impression about the characters. Cullen, to my surprise, is someone I came to trust, while Vivienne simply earned my ire.