You probably don't know this about me, I don't discuss it much here, but my day job is a technical writer. Which means, I write white papers, blogs, training materials, and all sorts of really boring stuff.
A thing you definitely don't know about me is that I have a whole college degree in writing from a university here in Texas. Meaning, I've been academically trained on how to write. It means that I've been trained on the key elements of effective writing- both fiction and technical- and I have well over a decade of experience in effective writing.
So, "keeping a personal bias in check" is certainly a hallmark of effective writing. Effective technical writing. In elementary & high school, they usually call it non-fiction writing. You have to scrub any sense of your personal voice from the final product, and in the corporate world I often have to write 'in the voice' of a specific VP or whatever so the blog or paper will sound like them. So, the things I write don't sound like me at all, and they certainly don't espouse my progressive politics.
However, in fiction writing, it's the exact opposite. You have to have a point of view- a bias- to tell a compelling story. All the good stories have a very clear point of view. You may not like it, not every story is for every person, but it has to be there.
Otherwise, it's boring and everyone forgets about it.
So, claiming that a fiction writer needs to "keep their bias in check" is wrong. It goes against the fundamental basis for writing fiction- have something to say and say it loudly.
However, saying that writers need to keep their bias in checkt is you demanding that writers tell stories you approve of. That's why you want her to "keep it in check" like your example of Rand or Orwell.
It's okay to like some stories and be offended by others. You can like or not like things all you want, that's okay. But expecting writers to produce works that you approve of?
Well, I have some bad news for you.
