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.
And why shouldn't I be allowed to criticise other cultures? We're all human.
I can and I will say what is right and wrong, I will not accept a call to tradition as a warranted reason for something to exist. If a female is married off at 6 then I will object. Do you know why? Becuase medically it can be shown that its damaging to a person that isn't fully developed. Logic, reason and EVIDENCE.
Why would the proponents of certain cultural practices need to hide behind cultural relatavism? Thats an attempt to shut down an argument for no good reason. Why be so insecure? If they think what they do is right, then they can argue it with me and if they can show me that, then fine. I will no longer resist something.