I loathe cultural relatavism.
I don't care what you're culture is, what you're religion is or what you're philosophical ideology is. If you do a practice that is harmful or an unwarranted restriction of a persons rights, and if this can be clearly shown through the use of logic, reason and evidence then I will condemn it at every single opportunity. I have no issue with the parts of culture that enrich life, such as art, music, food, dance, architecture etc. But the moment something is overtly harmful, an instrument of segregation, an unwarranted restriction of rights etc then you will find me in opposition intellectually.
If a behavior is warranted as being criminal than it will be fought against by either followers of other cultures or by members of that religion, culture, or school of thought. Someway or somehow, hopefully. Although I understand the argument you are trying to make you certainly just cannot view the world by saying this is right and this is wrong. This type of view will just obstruct your logical reasoning behind as to why they are being performed and to how it began et cetera, et cetera, and et cetera.
Cultures throughout the world aren't perfect. There are good and bad aspects about each of them, but to simply say that a person's decision isn't influenced by a certain portion of the culture that they reside in isn't really right. Its much easier to just say that such and such is wrong then leave it be. Quite understandable.