Academic philosophy is very white...

...but this seems to me an unlikely explanation, because it isn't how work is actually evaluated (at least not in the fields I've worked in over the years).  Armchair speculation like this, unhinged from actual evidence, and especially when circulated in the popular media which thrives on nonsense like this, doesn't seem very helpful for the field in terms of remeding the situation.  This is also relevant, though not philosophy-specific.