Taking influence from other cultures is hardly appropriation.  It contributes to a shared experience so that we may understand each other better.

If we decide that an artist is only permitted to draw from his/her own heritage for influence, imagine how bleak the creative landscape would be.  Opera would cease to exist, since virtually all of the stories upon which the classics are based are lifted from other cultures .  Goodbye rock'n'roll, blues and jazz.  No more Doric columns in architecture, unbelievably bland food in the kitchens and cafés, and literature confined to the Western experience.

And if we want to get truly ridiculous about the whole thing -- indigenous writing, which sparked this whole non-debate, may be called cultural appropriation of the worst sort.  Few if any indigenous peoples even had a written language -- and the oral traditions did not begin with English.  For shame!