Because of the existence of "human rights," I believe we can agree that there are some expectations that cross cultural boundaries. Misogyny, homophobia, etc have no reason to be tolerated. They are moral issues and deserve to be discussed without anything being justified by "it's just what they do." Aspects of culture without any moral ties (clothing, etc), however, CAN be justified with that.
Well some things we tend to see as "human rights", "basic decency" or "common sense" clearly vary between cultures. Heck, even within our own culture.
Also it's not all that theoretical, it's about problems in practical situations. For example, I know a lot of teachers, who hear stuff like "you can't tell me anything because you're a woman", "there are no gay [insert ethnicity]" and stuff like that from very young students. Also it's difficult to explain why the Holocaust is a bad thing (still pretty relevant in Germany) to students who not only have no personal connection to it, but also have grown up with "Israel is the devil" propaganda.
As to "Aspects of culture without any moral ties (clothing, etc)" - how can you tell if a headscarf is worn out of free will or due to cultural pressure? It could be an expression of religious belief, or a symbol of misogynistic repression.
How do you deal with parents who don't want their daughters to participate in swimming classes or other activities? (Apparently you make them wear
a burkini, point is, it's not that easy.)