You know, to steal something one must deprive the rightful owner of its use.  Writing from the vantage point of someone from different cultures/sub-cultures or expressing views with respect to different cultures does not deprive members of such cultures/sub-cultures from expressing their own views.  In any event, the sad reality is that such "appropriation" has also been beneficial to the cultures appropriated.  Non-aboriginal writers writing with an aboriginal voice have made many aware of the systemic abuses against aboriginals.  Just as white musicians--by "appropriating" the music of  the black community--brought attention to that community and were instrumental in ensuring that black musicians were recognized and honoured.  One could argue that it is lamentable that such "appropriation" was required in the first place, but the unfortunate reality is that it was, and that it did have a positive effect on recognition of the cultures appropriated.