The relativists defense here is something like Ned is a "victim" of his time, when misogyny woven into the fabric of society. This defense is totally inadequate to me. This kind of reasoning basically silences minority voices, usually the victims themselves and also the conscientious few who speak out in moral outrage. Let's take the Civil Rights Movements in the U.S. I have family aging family members who hold very racist ideas because they were born in a time when those ideas were commonplace and accepted. Is that a valid excuse? No. Because then I'm essentially saying "everyone thought that way" when in reality everyone did not. It's like ignoring all the people who marched and protested and did freedom rides in opposition to an unjust system (and lest we forget a lot of those people died because of these efforts). You're whitewashing them from history like they didn't exist. The same could be said for the abolitionists before the Civil War.
Take it back to Westeros and gender norms. There are people like Arya and Brienne who do not live up to the expectations society places on them. Brienne in particular feels the full brunt of the society's misogyny and but still perseveres. She's an awesome character. I love her. But to forgive the Ned Starks and Robert Baratheons et al. for dishing out the abuse she receives because that's the cultural norm? Absolutely unforgivable. Because there are people who don't subscribe to these fucked up norms. Her name is Brienne.
Easy tiger! By this rationale, every character is 'absolutely unforgivable' when you apply your modern morality. Nearly everyone subscribes to gender roles in general. You mention Arya and Brienne, what's interesting about them is that they aren't feminists pushing for or even espousing a belief in different gender roles, all they do is refuse themselves to do what is expected of them. They don't say 'this is wrong, girls shouldn't be made to act this way.' they are perfectly accepting of everyone else continuing on as before, only that they won't abide by those same conventions. The actual only example in westeros would be in dorne where gender roles are truly different and one could argue much closer to a modern day view. There is no feminist movement afoot in Westeros that supports your analogy to the civil rights movement that your relatives lived through.
Isn't this exactly the same as saying that every single human being who believed that the world was flat was an absolute fool to think so, because it turns out it aint? That the second one person said, 'hey wait a second, i'm not so sure' that absent immediate adoption of that viewpoint, they should be viewed in hindsight as morons?
Look at how every single character accepts a class structure of lords and monarchs with absolute power over the common man. Isn't this 'absolutely unforgivable' when looked at through a 21st century prism where individual rights are promoted and protected? Dany, your champion of feminist might, is an interesting character in this instance, as she may not be forcing anyone to follow or be subservient to her, but were the society different, the people would not be doing so. It is a society of kings or queens and their subjects, what the little people know how to do is to follow so that is what they do. Every one of them that does so is accepting the same social structure that we in the modern day find reprehensible.