The mainstream certainly would have the most influence.....
British Vogue hasnt even featured a black model on the cover since 2002 and that Aug 2002 issue featured Naomi Campbell- she had attacked British Vogue for being extremely racist and sidelining black models.
There was the recent incident of Naomi being fined for the British Airways attack when she accused them of being racist...
The sad thing about racism in fashion specifically is that the implication is that brands, magazines etc do not see black models as beautiful and are not as appreciative of black beauty as they are of other forms of beauty or things that they are so willing to put in their ads/magazines/strategies