"What I've written here is likely to be contentious."

Not in my mind, Elizabeth.  One thing IS contentious (although you may not have written it): the headline. "Why can't we debate it?"  I`ll tell you why: because debating the ridiculous notion of appropriation gives it far more credit than it deserves.  Taken to its extreme (such as the Writers' Union reaction) fear-of-appropriation will result stifling creative works of all kinds.  

I speak as a writer.  As a writer, I don't give a d*** if any indigenous author wants to write about white people.  It'd likely be a refreshing take. How DO they really see us, in various circumstances?  I've written--in both non-fiction and fiction works--about 19th century First Nations people.  I`ve written about 20th century Mexicans and Americans, too, and  I give them both absolute freedom to write about Canadians.  But they don`t need my blessing or anybody else`s.

"Write what you don’t know," says author Niedzviecki. Absolutely.