I've always said that the most fun thing about writing is that I can be me -- or anyone else. When the writer is automatically expected to embody all sorts of impossible creatures, the question of 'who gets to write who/what' has no more power. We will have grown as a nation of readers when we can accept humans exploring humanity as an entire subject, instead of expecting each group to limit themselves to an incremental examination of their perceived ethnicity.
It's good to know that the same concept exists in the realms of other writers such as the talented Sid Fleischman. This nifty quote is on his biography page.